History of Science - Henry Smith Williams - 1910 - Vol-04

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History of Science ·

Williams, Henry Smith (Autor) · New York 1910 (1910)

Herausgeber: Harper & Brothers · Verlag:  · (Ed)
ISBN/ISBN13:1404307311/9781404307315 · ISSN:
Sprache: English · Version: v1.00 (Volltext)
Wissenschaftsgeschichte, Science History
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Williams, Henry Smith: History of Science . In: eLib.at (Hrg.), 26. Juni 2022. URL: http://elib.at/
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Geschichte · Technik · Wissenschaftsgeschichte · Technikgeschichte · Science History
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AS regards chronology, the epoch covered in the present volume is identical with that viewed in the preceding one. But now as regards subject matter we pass on to those diverse phases of the physical world which are the field of the chemist, and to those yet more intricate processes which have to do with living organisms. So radical are the changes here that we seem to be entering new worlds; and yet, here as before, there are intimations of the new discoveries away back in the Greek days. The solution of the problem of respiration will remind us that Anaxagoras half guessed the secret; and in those diversified studies which tell us of the Daltonian atom in its wonderful transmutations, we shall be reminded again of the Clazomenian philosopher and his successor Democritus.

Yet we should press the analogy much too far were we to intimate that the Greek of the elder day or any thinker of a more recent period had penetrated, even in the vaguest way, all of the mysteries that the nineteenth century has revealed in the fields of chemistry and biology. At the very most the insight of those great Greeks and of the wonderful seventeenth-century philosophers who so often seemed on the verge of our later discoveries did no more than vaguely anticipate their successors of this later century. To gain an accurate, really specific knowledge of the properties of elementary bodies was reserved for the chemists of a recent epoch. The vague Greek questionings as to organic evolution were world-wide from the precise inductions of a Darwin. If the mediaeval Arabian endeavored to dull the knife of the surgeon with the use of drugs, his results hardly merit to be termed even an anticipation of modern anaesthesia. And when we speak of preventive medicine--of bacteriology in all its phases--we have to do with a marvellous field of which no previous generation of men had even the slightest inkling.

All in all, then, those that lie before us are perhaps the most wonderful and the most fascinating of all the fields of science. As the chapters of the preceding book carried us out into a macrocosm of inconceivable magnitude, our present studies are to reveal a microcosm of equally inconceivable smallness. As the studies of the physicist attempted to reveal the very nature of matter and of energy, we have now to seek the solution of the yet more inscrutable problems of life and of mind.


The development of the science of chemistry from the "science" of alchemy is a striking example of the complete revolution in the attitude of observers in the field of science. As has been pointed out in a preceding chapter, the alchemist, having a preconceived idea of how things should be, made all his experiments to prove his preconceived theory; while the chemist reverses this attitude of mind and bases his conceptions on the results of his laboratory experiments. In short, chemistry is what alchemy never could be, an inductive science. But this transition from one point of view to an exactly opposite one was necessarily a very slow process. Ideas that have held undisputed sway over the minds of succeeding generations for hundreds of years cannot be overthrown in a moment, unless the agent of such an overthrow be so obvious that it cannot be challenged. The rudimentary chemistry that overthrew alchemy had nothing so obvious and palpable.

The great first step was the substitution of the one principle, phlogiston, for the three principles, salt, sulphur, and mercury. We have seen how the experiment of burning or calcining such a metal as lead "destroyed" the lead as such, leaving an entirely different substance in its place, and how the original metal could be restored by the addition of wheat to the calcined product. To the alchemist this was "mortification" and "revivification" of the metal. For, as pointed out by Paracelsus, "anything that could be killed by man could also be revivified by him, although this was not possible to the things killed by God." The burning of such substances as wood, wax, oil, etc., was also looked upon as the same "killing" process, and the fact that the alchemist was unable to revivify them was regarded as simply the lack of skill on his part, and in no wise affecting the theory itself.

But the iconoclastic spirit, if not the acceptance of all the teachings, of the great Paracelsus had been gradually taking root among the better class of alchemists, and about the middle of the seventeenth century Robert Boyle (1626-1691) called attention to the possibility of making a wrong deduction from the phenomenon of the calcination of the metals, because of a very important factor, the action of the air, which was generally overlooked. And he urged his colleagues of the laboratories to give greater heed to certain other phenomena that might pass unnoticed in the ordinary calcinating process. In his work, The Sceptical Chemist, he showed the reasons for doubting the threefold constitution of matter; and in his General History of the Air advanced some novel and carefully studied theories as to the composition of the atmosphere. This was an important step, and although Boyle is not directly responsible for the phlogiston theory, it is probable that his experiments on the atmosphere influenced considerably the real founders, Becker and Stahl.

Boyle gave very definitely his idea of how he thought air might be composed. "I conjecture that the atmospherical air consists of three different kinds of corpuscles," he says; "the first, those numberless particles which, in the form of vapors or dry exhalations, ascend from the earth, water, minerals, vegetables, animals, etc.; in a word, whatever substances are elevated by the celestial or subterraneal heat, and thence diffused into the atmosphere. The second may be yet more subtle, and consist of those exceedingly minute atoms, the magnetical effluvia of the earth, with other innumerable particles sent out from the bodies of the celestial luminaries, and causing, by their influence, the idea of light in us. The third sort is its characteristic and essential property, I mean permanently elastic parts. Various hypotheses may be framed relating to the structure of these later particles of the air. They might be resembled to the springs of watches, coiled up and endeavoring to restore themselves; to wool, which, being compressed, has an elastic force; to slender wires of different substances, consistencies, lengths, and thickness; in greater curls or less, near to, or remote from each other, etc., yet all continuing springy, expansible, and compressible. Lastly, they may also be compared to the thin shavings of different kinds of wood, various in their lengths, breadth, and thickness. And this, perhaps, will seem the most eligible hypothesis, because it, in some measure, illustrates the production of the elastic particles we are considering. For no art or curious instruments are required to make these shavings whose curls are in no wise uniform, but seemingly casual; and what is more remarkable, bodies that before seemed unelastic, as beams and blocks, will afford them."[1]

Although this explanation of the composition of the air is most crude, it had the effect of directing attention to the fact that the atmosphere is not "mere nothingness," but a "something" with a definite composition, and this served as a good foundation for future investigations. To be sure, Boyle was neither the first nor the only chemist who had suspected that the air was a mixture of gases, and not a simple one, and that only certain of these gases take part in the process of calcination. Jean Rey, a French physician, and John Mayow, an Englishman, had preformed experiments which showed conclusively that the air was not a simple substance; but Boyle's work was better known, and in its effect probably more important. But with all Boyle's explanations of the composition of air, he still believed that there was an inexplicable something, a "vital substance," which he was unable to fathom, and which later became the basis of Stahl's phlogiston theory. Commenting on this mysterious substance, Boyle says: "The, difficulty we find in keeping flame and fire alive, though but for a little time, without air, renders it suspicious that there be dispersed through the rest of the atmosphere some odd substance, either of a solar, astral, or other foreign nature; on account of which the air is so necessary to the substance of flame!" It was this idea that attracted the attention of George Ernst Stahl (1660-1734), a professor of medicine in the University of Halle, who later founded his new theory upon it. Stahl's theory was a development of an earlier chemist, Johann Joachim Becker (1635-1682), in whose footsteps he followed and whose experiments he carried further.

In many experiments Stahl had been struck with the fact that certain substances, while differing widely, from one another in many respects, were alike in combustibility. From this he argued that all combustible substances must contain a common principle, and this principle he named phlogiston. This phlogiston he believed to be intimately associated in combination with other substances in nature, and in that condition not perceivable by the senses; but it was supposed to escape as a substance burned, and become apparent to the senses as fire or flame. In other words, phlogiston was something imprisoned in a combustible structure (itself forming part of the structure), and only liberated when this structure was destroyed. Fire, or flame, was FREE phlogiston, while the imprisoned phlogiston was called COMBINED PHLOGISTON, or combined fire. The peculiar quality of this strange substance was that it disliked freedom and was always striving to conceal itself in some combustible substance. Boyle's tentative suggestion that heat was simply motion was apparently not accepted by Stahl, or perhaps it was unknown to him.

According to the phlogistic theory, the part remaining after a substance was burned was simply the original substance deprived of phlogiston. To restore the original combustible substance, it was necessary to heat the residue of the combustion with something that burned easily, so that the freed phlogiston might again combine with the ashes. This was explained by the supposition that the more combustible a substance was the more phlogiston it contained, and since free phlogiston sought always to combine with some suitable substance, it was only necessary to mix the phlogisticating agents, such as charcoal, phosphorus, oils, fats, etc., with the ashes of the original substance, and heat the mixture, the phlogiston thus freed uniting at once with the ashes. This theory fitted very nicely as applied to the calcined lead revivified by the grains of wheat, although with some other products of calcination it did not seem to apply at all.

It will be seen from this that the phlogistic theory was a step towards chemistry and away from alchemy. It led away from the idea of a "spirit" in metals that could not be seen, felt, or appreciated by any of the senses, and substituted for it a principle which, although a falsely conceived one, was still much more tangible than the "spirit," since it could be seen and felt as free phlogiston and weighed and measured as combined phlogiston. The definiteness of the statement that a metal, for example, was composed of phlogiston and an element was much less enigmatic, even if wrong, than the statement of the alchemist that "metals are produced by the spiritual action of the three principles, salt, mercury, sulphur"--particularly when it is explained that salt, mercury, and sulphur were really not what their names implied, and that there was no universally accepted belief as to what they really were.

The metals, which are now regarded as elementary bodies, were

considered compounds by the phlogistians, and they believed that

the calcining of a metal was a process of simplification. They

noted, however, that the remains of calcination weighed more than

the original product, and the natural inference from this would

be that the metal must have taken in some substance rather than

have given off anything. But the phlogistians had not learned

the all-important significance of weights, and their explanation

of variation in weight was either that such gain or loss was an

unimportant "accident" at best, or that phlogiston, being light,

tended to lighten any substance containing it, so that driving it

out of the metal by calcination naturally left the residue


At first the phlogiston theory seemed to explain in an

indisputable way all the known chemical phenomena. Gradually,

however, as experiments multiplied, it became evident that the

plain theory as stated by Stahl and his followers failed to

explain satisfactorily certain laboratory reactions. To meet

these new conditions, certain modifications were introduced from

time to time, giving the theory a flexibility that would allow it

to cover all cases. But as the number of inexplicable experiments

continued to increase, and new modifications to the theory became

necessary, it was found that some of these modifications were

directly contradictory to others, and thus the simple theory

became too cumbersome from the number of its modifications. Its

supporters disagreed among themselves, first as to the

explanation of certain phenomena that did not seem to accord with

the phlogistic theory, and a little later as to the theory

itself. But as yet there was no satisfactory substitute for this

theory, which, even if unsatisfactory, seemed better than

anything that had gone before or could be suggested.

But the good effects of the era of experimental research, to

which the theory of Stahl had given such an impetus, were showing

in the attitude of the experimenters. The works of some of the

older writers, such as Boyle and Hooke, were again sought out in

their dusty corners and consulted, and their surmises as to the

possible mixture of various gases in the air were more carefully

considered. Still the phlogiston theory was firmly grounded in

the minds of the philosophers, who can hardly be censured for

adhering to it, at least until some satisfactory substitute was

offered. The foundation for such a theory was finally laid, as

we shall see presently, by the work of Black, Priestley,

Cavendish, and Lavoisier, in the eighteenth century, but the

phlogiston theory cannot be said to have finally succumbed until

the opening years of the nineteenth century.



Modern chemistry may be said to have its beginning with the work

of Stephen Hales (1677-1761), who early in the eighteenth century

began his important study of the elasticity of air. Departing

from the point of view of most of the scientists of the time, be

considered air to be "a fine elastic fluid, with particles of

very different nature floating in it" ; and he showed that these

"particles" could be separated. He pointed out, also, that

various gases, or "airs," as he called them, were contained in

many solid substances. The importance of his work, however, lies

in the fact that his general studies were along lines leading

away from the accepted doctrines of the time, and that they gave

the impetus to the investigation of the properties of gases by

such chemists as Black, Priestley, Cavendish, and Lavoisier,

whose specific discoveries are the foundation-stones of modern



The careful studies of Hales were continued by his younger

confrere, Dr. Joseph Black (1728-1799), whose experiments in the

weights of gases and other chemicals were first steps in

quantitative chemistry. But even more important than his

discoveries of chemical properties in general was his discovery

of the properties of carbonic-acid gas.

Black had been educated for the medical profession in the

University of Glasgow, being a friend and pupil of the famous Dr.

William Cullen. But his liking was for the chemical laboratory

rather than for the practice of medicine. Within three years

after completing his medical course, and when only twenty-three

years of age, he made the discovery of the properties of carbonic

acid, which he called by the name of "fixed air." After

discovering this gas, Black made a long series of experiments, by

which he was able to show how widely it was distributed

throughout nature. Thus, in 1757, be discovered that the bubbles

given off in the process of brewing, where there was vegetable

fermentation, were composed of it. To prove this, he collected

the contents of these bubbles in a bottle containing lime-water.

When this bottle was shaken violently, so that the lime-water and

the carbonic acid became thoroughly mixed, an insoluble white

powder was precipitated from the solution, the carbonic acid

having combined chemically with the lime to form the insoluble

calcium carbonate, or chalk. This experiment suggested another.

Fixing a piece of burning charcoal in the end of a bellows, he

arranged a tube so that the gas coming from the charcoal would

pass through the lime-water, and, as in the case of the bubbles

from the brewer's vat, he found that the white precipitate was

thrown down; in short, that carbonic acid was given off in

combustion. Shortly after, Black discovered that by blowing

through a glass tube inserted into lime-water, chalk was

precipitated, thus proving that carbonic acid was being

constantly thrown off in respiration.

The effect of Black's discoveries was revolutionary, and the

attitude of mind of the chemists towards gases, or "airs," was

changed from that time forward. Most of the chemists, however,

attempted to harmonize the new facts with the older theories--to

explain all the phenomena on the basis of the phlogiston theory,

which was still dominant. But while many of Black's discoveries

could not be made to harmonize with that theory, they did not

directly overthrow it. It required the additional discoveries of

some of Black's fellow-scientists to complete its downfall, as we

shall see.


This work of Black's was followed by the equally important work

of his former pupil, Henry Cavendish (1731-1810), whose discovery

of the composition of many substances, notably of nitric acid and

of water, was of great importance, adding another link to the

important chain of evidence against the phlogiston theory.

Cavendish is one of the most eccentric figures in the history of

science, being widely known in his own time for his immense

wealth and brilliant intellect, and also for his peculiarities

and his morbid sensibility, which made him dread society, and

probably did much in determining his career. Fortunately for him,

and incidentally for the cause of science, he was able to pursue

laboratory investigations without being obliged to mingle with

his dreaded fellow-mortals, his every want being provided for by

the immense fortune inherited from his father and an uncle.

When a young man, as a pupil of Dr. Black, he had become imbued

with the enthusiasm of his teacher, continuing Black's

investigations as to the properties of carbonic-acid gas when

free and in combination. One of his first investigations was

reported in 1766, when he communicated to the Royal Society his

experiments for ascertaining the properties of carbonic-acid and

hydrogen gas, in which he first showed the possibility of

weighing permanently elastic fluids, although Torricelli had

before this shown the relative weights of a column of air and a

column of mercury. Other important experiments were continued by

Cavendish, and in 1784 he announced his discovery of the

composition of water, thus robbing it of its time-honored

position as an "element." But his claim to priority in this

discovery was at once disputed by his fellow-countryman James

Watt and by the Frenchman Lavoisier. Lavoisier's claim was soon

disallowed even by his own countrymen, but for many years a

bitter controversy was carried on by the partisans of Watt and

Cavendish. The two principals, however, seem. never to have

entered into this controversy with anything like the same ardor

as some of their successors, as they remained on the best of

terms.[1] It is certain, at any rate, that Cavendish announced

his discovery officially before Watt claimed that the

announcement had been previously made by him, "and, whether right

or wrong, the honor of scientific discoveries seems to be

accorded naturally to the man who first publishes a demonstration

of his discovery." Englishmen very generally admit the justness

of Cavendish's claim, although the French scientist Arago, after

reviewing the evidence carefully in 1833, decided in favor of


It appears that something like a year before Cavendish made known

his complete demonstration of the composition of water, Watt

communicated to the Royal Society a suggestion that water was

composed of "dephlogisticated air (oxygen) and phlogiston

(hydrogen) deprived of part of its latent heat." Cavendish knew

of the suggestion, but in his experiments refuted the idea that

the hydrogen lost any of its latent heat. Furthermore, Watt

merely suggested the possible composition without proving it,

although his idea was practically correct, if we can rightly

interpret the vagaries of the nomenclature then in use. But had

Watt taken the steps to demonstrate his theory, the great "Water

Controversy" would have been avoided. Cavendish's report of his

discovery to the Royal Society covers something like forty pages

of printed matter. In this he shows how, by passing an electric

spark through a closed jar containing a mixture of hydrogen gas

and oxygen, water is invariably formed, apparently by the union

of the two gases. The experiment was first tried with hydrogen

and common air, the oxygen of the air uniting with the hydrogen

to form water, leaving the nitrogen of the air still to be

accounted for. With pure oxygen and hydrogen, however, Cavendish

found that pure water was formed, leaving slight traces of any

other, substance which might not be interpreted as being Chemical

impurities. There was only one possible explanation of this

phenomenon--that hydrogen and oxygen, when combined, form water.

"By experiments with the globe it appeared," wrote Cavendish,

"that when inflammable and common air are exploded in a proper

proportion, almost all the inflammable air, and near one-fifth

the common air, lose their elasticity and are condensed into dew.

And by this experiment it appears that this dew is plain water,

and consequently that almost all the inflammable air is turned

into pure water.

"In order to examine the nature of the matter condensed on firing

a mixture of dephlogisticated and inflammable air, I took a glass

globe, holding 8800 grain measures, furnished with a brass cock

and an apparatus for firing by electricity. This globe was well

exhausted by an air-pump, and then filled with a mixture of

inflammable and dephlogisticated air by shutting the cock,

fastening the bent glass tube into its mouth, and letting up the

end of it into a glass jar inverted into water and containing a

mixture of 19,500 grain measures of dephlogisticated air, and

37,000 of inflammable air; so that, upon opening the cock, some

of this mixed air rushed through the bent tube and filled the

globe. The cock was then shut and the included air fired by

electricity, by means of which almost all of it lost its

elasticity (was condensed into water vapors). The cock was then

again opened so as to let in more of the same air to supply the

place of that destroyed by the explosion, which was again fired,

and the operation continued till almost the whole of the mixture

was let into the globe and exploded. By this means, though the

globe held not more than a sixth part of the mixture, almost the

whole of it was exploded therein without any fresh exhaustion of

the globe."

At first this condensed matter was "acid to the taste and

contained two grains of nitre," but Cavendish, suspecting that

this was due to impurities, tried another experiment that proved

conclusively that his opinions were correct. "I therefore made

another experiment," he says, "with some more of the same air

from plants in which the proportion of inflammable air was

greater, so that the burnt air was almost completely

phlogisticated, its standard being one-tenth. The condensed

liquor was then not at all acid, but seemed pure water."

From these experiments he concludes "that when a mixture of

inflammable and dephlogisticated air is exploded, in such

proportions that the burnt air is not much phlogisticated, the

condensed liquor contains a little acid which is always of the

nitrous kind, whatever substance the dephlogisticated air is

procured from; but if the proportion be such that the burnt air

is almost entirely phlogisticated, the condensed liquor is not at

all acid, but seems pure water, without any addition


These same experiments, which were undertaken to discover the

composition of water, led him to discover also the composition of

nitric acid. He had observed that, in the combustion of hydrogen

gas with common air, the water was slightly tinged with acid, but

that this was not the case when pure oxygen gas was used. Acting

upon this observation, he devised an experiment to determine the

nature of this acid. He constructed an apparatus whereby an

electric spark was passed through a vessel containing common air.

After this process had been carried on for several weeks a small

amount of liquid was formed. This liquid combined with a solution

of potash to form common nitre, which "detonated with charcoal,

sparkled when paper impregnated with it was burned, and gave out

nitrous fumes when sulphuric acid was poured on it." In other

words, the liquid was shown to be nitric acid. Now, since nothing

but pure air had been used in the initial experiment, and since

air is composed of nitrogen and oxygen, there seemed no room to

doubt that nitric acid is a combination of nitrogen and oxygen.

This discovery of the nature of nitric acid seems to have been

about the last work of importance that Cavendish did in the field

of chemistry, although almost to the hour of his death he was

constantly occupied with scientific observations. Even in the

last moments of his life this habit asserted itself, according to

Lord Brougham. "He died on March 10, 1810, after a short

illness, probably the first, as well as the last, which he ever

suffered. His habit of curious observation continued to the end.

He was desirous of marking the progress of the disease and the

gradual extinction of the vital powers. With these ends in view,

that he might not be disturbed, he desired to be left alone. His

servant, returning sooner than he had wished, was ordered again

to leave the chamber of death, and when be came back a second

time he found his master had expired.[3]


While the opulent but diffident Cavendish was making his

important discoveries, another Englishman, a poor country

preacher named Joseph Priestley (1733-1804) was not only

rivalling him, but, if anything, outstripping him in the pursuit

of chemical discoveries. In 1761 this young minister was given a

position as tutor in a nonconformist academy at Warrington, and

here, for six years, he was able to pursue his studies in

chemistry and electricity. In 1766, while on a visit to London,

he met Benjamin Franklin, at whose suggestion he published his

History of Electricity. From this time on he made steady

progress in scientific investigations, keeping up his

ecclesiastical duties at the same time. In 1780 he removed to

Birmingham, having there for associates such scientists as James

Watt, Boulton, and Erasmus Darwin.

Eleven years later, on the anniversary of the fall of the Bastile

in Paris, a fanatical mob, knowing Priestley's sympathies with

the French revolutionists, attacked his house and chapel, burning

both and destroying a great number of valuable papers and

scientific instruments. Priestley and his family escaped violence

by flight, but his most cherished possessions were destroyed; and

three years later he quitted England forever, removing to the

United States, whose struggle for liberty he had championed. The

last ten years of his life were spent at Northumberland,

Pennsylvania, where he continued his scientific researches.

Early in his scientific career Priestley began investigations

upon the "fixed air" of Dr. Black, and, oddly enough, he was

stimulated to this by the same thing that had influenced

Black--that is, his residence in the immediate neighborhood of a

brewery. It was during the course of a series of experiments on

this and other gases that he made his greatest discovery, that of

oxygen, or "dephlogisticated air," as he called it. The story of

this important discovery is probably best told in Priestley's own


"There are, I believe, very few maxims in philosophy that have

laid firmer hold upon the mind than that air, meaning atmospheric

air, is a simple elementary substance, indestructible and

unalterable, at least as much so as water is supposed to be. In

the course of my inquiries I was, however, soon satisfied that

atmospheric air is not an unalterable thing; for that, according

to my first hypothesis, the phlogiston with which it becomes

loaded from bodies burning in it, and the animals breathing it,

and various other chemical processes, so far alters and depraves

it as to render it altogether unfit for inflammation,

respiration, and other purposes to which it is subservient; and I

had discovered that agitation in the water, the process of

vegetation, and probably other natural processes, restore it to

its original purity....

"Having procured a lens of twelve inches diameter and twenty

inches local distance, I proceeded with the greatest alacrity, by

the help of it, to discover what kind of air a great variety of

substances would yield, putting them into the vessel, which I

filled with quicksilver, and kept inverted in a basin of the same

.... With this apparatus, after a variety of experiments .... on

the 1st of August, 1774, I endeavored to extract air from

mercurius calcinatus per se; and I presently found that, by means

of this lens, air was expelled from it very readily. Having got

about three or four times as much as the bulk of my materials, I

admitted water to it, and found that it was not imbibed by it.

But what surprised me more than I can express was that a candle

burned in this air with a remarkably vigorous flame, very much

like that enlarged flame with which a candle burns in nitrous

oxide, exposed to iron or liver of sulphur; but as I had got

nothing like this remarkable appearance from any kind of air

besides this particular modification of vitrous air, and I knew

no vitrous acid was used in the preparation of mercurius

calcinatus, I was utterly at a loss to account for it."[4]

The "new air" was, of course, oxygen. Priestley at once

proceeded to examine it by a long series of careful experiments,

in which, as will be seen, he discovered most of the remarkable

qualities of this gas. Continuing his description of these

experiments, he says:

"The flame of the candle, besides being larger, burned with more

splendor and heat than in that species of nitrous air; and a

piece of red-hot wood sparkled in it, exactly like paper dipped

in a solution of nitre, and it consumed very fast; an experiment

that I had never thought of trying with dephlogisticated nitrous


". . . I had so little suspicion of the air from the mercurius

calcinatus, etc., being wholesome, that I had not even thought of

applying it to the test of nitrous air; but thinking (as my

reader must imagine I frequently must have done) on the candle

burning in it after long agitation in water, it occurred to me at

last to make the experiment; and, putting one measure of nitrous

air to two measures of this air, I found not only that it was

diminished, but that it was diminished quite as much as common

air, and that the redness of the mixture was likewise equal to a

similar mixture of nitrous and common air.... The next day I was

more surprised than ever I had been before with finding that,

after the above-mentioned mixture of nitrous air and the air from

mercurius calcinatus had stood all night, . . . a candle burned

in it, even better than in common air."

A little later Priestley discovered that "dephlogisticated air .

. . is a principal element in the composition of acids, and may

be extracted by means of heat from many substances which contain

them.... It is likewise produced by the action of light upon

green vegetables; and this seems to be the chief means employed

to preserve the purity of the atmosphere."

This recognition of the important part played by oxygen in the

atmosphere led Priestley to make some experiments upon mice and

insects, and finally upon himself, by inhalations of the pure

gas. "The feeling in my lungs," he said, "was not sensibly

different from that of common air, but I fancied that my

breathing felt peculiarly light and easy for some time

afterwards. Who can tell but that in time this pure air may

become a fashionable article in luxury? . . . Perhaps we may from

these experiments see that though pure dephlogisticated air might

be useful as a medicine, it might not be so proper for us in the

usual healthy state of the body."

This suggestion as to the possible usefulness of oxygen as a

medicine was prophetic. A century later the use of oxygen had

become a matter of routine practice with many physicians. Even in

Priestley's own time such men as Dr. John Hunter expressed their

belief in its efficacy in certain conditions, as we shall see,

but its value in medicine was not fully appreciated until several

generations later.

Several years after discovering oxygen Priestley thus summarized

its properties: "It is this ingredient in the atmospheric air

that enables it to support combustion and animal life. By means

of it most intense heat may be produced, and in the purest of it

animals will live nearly five times as long as in an equal

quantity of atmospheric air. In respiration, part of this air,

passing the membranes of the lungs, unites with the blood and

imparts to it its florid color, while the remainder, uniting with

phlogiston exhaled from venous blood, forms mixed air. It is

dephlogisticated air combined with water that enables fishes to

live in it."[5]


The discovery of oxygen was the last but most important blow to

the tottering phlogiston theory, though Priestley himself would

not admit it. But before considering the final steps in the

overthrow of Stahl's famous theory and the establishment of

modern chemistry, we must review the work of another great

chemist, Karl Wilhelm Scheele (1742-1786), of Sweden, who

discovered oxygen quite independently, although later than

Priestley. In the matter of brilliant discoveries in a brief

space of time Scheele probably eclipsed all his great

contemporaries. He had a veritable genius for interpreting

chemical reactions and discovering new substances, in this

respect rivalling Priestley himself. Unlike Priestley, however,

he planned all his experiments along the lines of definite

theories from the beginning, the results obtained being the

logical outcome of a predetermined plan.

Scheele was the son of a merchant of Stralsund, Pomerania, which

then belonged to Sweden. As a boy in school he showed so little

aptitude for the study of languages that he was apprenticed to an

apothecary at the age of fourteen. In this work he became at

once greatly interested, and, when not attending to his duties in

the dispensary, he was busy day and night making experiments or

studying books on chemistry. In 1775, still employed as an

apothecary, he moved to Stockholm, and soon after he sent to

Bergman, the leading chemist of Sweden, his first discovery--that

of tartaric acid, which he had isolated from cream of tartar.

This was the beginning of his career of discovery, and from that

time on until his death he sent forth accounts of new discoveries

almost uninterruptedly. Meanwhile he was performing the duties of

an ordinary apothecary, and struggling against poverty. His

treatise upon Air and Fire appeared in 1777. In this remarkable

book he tells of his discovery of oxygen--"empyreal" or

"fire-air," as he calls it--which he seems to have made

independently and without ever having heard of the previous

discovery by Priestley. In this book, also, he shows that air is

composed chiefly of oxygen and nitrogen gas.

Early in his experimental career Scheele undertook the solution

of the composition of black oxide of manganese, a substance that

had long puzzled the chemists. He not only succeeded in this,

but incidentally in the course of this series of experiments he

discovered oxygen, baryta, and chlorine, the last of far greater

importance, at least commercially, than the real object of his

search. In speaking of the experiment in which the discovery was

made he says:

"When marine (hydrochloric) acid stood over manganese in the cold

it acquired a dark reddish-brown color. As manganese does not

give any colorless solution without uniting with phlogiston

[probably meaning hydrogen], it follows that marine acid can

dissolve it without this principle. But such a solution has a

blue or red color. The color is here more brown than red, the

reason being that the very finest portions of the manganese,

which do not sink so easily, swim in the red solution; for

without these fine particles the solution is red, and red mixed

with black is brown. The manganese has here attached itself so

loosely to acidum salis that the water can precipitate it, and

this precipitate behaves like ordinary manganese. When, now, the

mixture of manganese and spiritus salis was set to digest, there

arose an effervescence and smell of aqua regis."[6]

The "effervescence" he refers to was chlorine, which he proceeded

to confine in a suitable vessel and examine more fully. He

described it as having a "quite characteristically suffocating

smell," which was very offensive. He very soon noted the

decolorizing or bleaching effects of this now product, finding

that it decolorized flowers, vegetables, and many other


Commercially this discovery of chlorine was of enormous

importance, and the practical application of this new chemical in

bleaching cloth soon supplanted the, old process of

crofting--that is, bleaching by spreading the cloth upon the

grass. But although Scheele first pointed out the bleaching

quality of his newly discovered gas, it was the French savant,

Berthollet, who, acting upon Scheele's discovery that the new gas

would decolorize vegetables and flowers, was led to suspect that

this property might be turned to account in destroying the color

of cloth. In 1785 he read a paper before the Academy of Sciences

of Paris, in which he showed that bleaching by chlorine was

entirely satisfactory, the color but not the substance of the

cloth being affected. He had experimented previously and found

that the chlorine gas was soluble in water and could thus be made

practically available for bleaching purposes. In 1786 James Watt

examined specimens of the bleached cloth made by Berthollet, and

upon his return to England first instituted the process of

practical bleaching. His process, however, was not entirely

satisfactory, and, after undergoing various modifications and

improvements, it was finally made thoroughly practicable by Mr.

Tennant, who hit upon a compound of chlorine and lime--the

chloride of lime--which was a comparatively cheap chemical

product, and answered the purpose better even than chlorine


To appreciate how momentous this discovery was to cloth

manufacturers, it should be remembered that the old process of

bleaching consumed an entire summer for the whitening of a single

piece of linen; the new process reduced the period to a few

hours. To be sure, lime had been used with fair success previous

to Tennant's discovery, but successful and practical bleaching by

a solution of chloride of lime was first made possible by him and

through Scheele's discovery of chlorine.

Until the time of Scheele the great subject of organic chemistry

had remained practically unexplored, but under the touch of his

marvellous inventive genius new methods of isolating and studying

animal and vegetable products were introduced, and a large number

of acids and other organic compounds prepared that had been

hitherto unknown. His explanations of chemical phenomena were

based on the phlogiston theory, in which, like Priestley, he

always, believed. Although in error in this respect, he was,

nevertheless, able to make his discoveries with extremely

accurate interpretations. A brief epitome of the list of some of

his more important discoveries conveys some idea, of his

fertility of mind as well as his industry. In 1780 he discovered

lactic acid,[7] and showed that it was the substance that caused

the acidity of sour milk; and in the same year he discovered

mucic acid. Next followed the discovery of tungstic acid, and in

1783 he added to his list of useful discoveries that of

glycerine. Then in rapid succession came his announcements of the

new vegetable products citric, malic, oxalic, and gallic acids.

Scheele not only made the discoveries, but told the world how he

had made them--how any chemist might have made them if he

chose--for he never considered that he had really discovered any

substance until he had made it, decomposed it, and made it again.

His experiments on Prussian blue are most interesting, not only

because of the enormous amount of work involved and the skill he

displayed in his experiments, but because all the time the

chemist was handling, smelling, and even tasting a compound of

one of the most deadly poisons, ignorant of the fact that the

substance was a dangerous one to handle. His escape from injury

seems almost miraculous; for his experiments, which were most

elaborate, extended over a considerable period of time, during

which he seems to have handled this chemical with impunity.

While only forty years of age and just at the zenith of his fame,

Scheele was stricken by a fatal illness, probably induced by his

ceaseless labor and exposure. It is gratifying to know, however,

that during the last eight or nine years of his life he had been

less bound down by pecuniary difficulties than before, as Bergman

had obtained for him an annual grant from the Academy. But it

was characteristic of the man that, while devoting one-sixth of

the amount of this grant to his personal wants, the remaining

five-sixths was devoted to the expense of his experiments.


The time was ripe for formulating the correct theory of chemical

composition: it needed but the master hand to mould the materials

into the proper shape. The discoveries in chemistry during the

eighteenth century had been far-reaching and revolutionary in

character. A brief review of these discoveries shows how

completely they had subverted the old ideas of chemical elements

and chemical compounds. Of the four substances earth, air, fire,

and water, for many centuries believed to be elementary bodies,

not one has stood the test of the eighteenth-century chemists.

Earth had long since ceased to be regarded as an element, and

water and air had suffered the same fate in this century. And

now at last fire itself, the last of the four "elements" and the

keystone to the phlogiston arch, was shown to be nothing more

than one of the manifestations of the new element, oxygen, and

not "phlogiston" or any other intangible substance.

In this epoch of chemical discoveries England had produced such

mental giants and pioneers in science as Black, Priestley, and

Cavendish; Sweden had given the world Scheele and Bergman, whose

work, added to that of their English confreres, had laid the

broad base of chemistry as a science; but it was for France to

produce a man who gave the final touches to the broad but rough

workmanship of its foundation, and establish it as the science of

modern chemistry. It was for Antoine Laurent Lavoisier

(1743-1794) to gather together, interpret correctly, rename, and

classify the wealth of facts that his immediate predecessors and

contemporaries had given to the world.

The attitude of the mother-countries towards these illustrious

sons is an interesting piece of history. Sweden honored and

rewarded Scheele and Bergman for their efforts; England received

the intellectuality of Cavendish with less appreciation than the

Continent, and a fanatical mob drove Priestley out of the

country; while France, by sending Lavoisier to the guillotine,

demonstrated how dangerous it was, at that time at least, for an

intelligent Frenchman to serve his fellowman and his country


"The revolution brought about by Lavoisier in science," says

Hoefer, "coincides by a singular act of destiny with another

revolution, much greater indeed, going on then in the political

and social world. Both happened on the same soil, at the same

epoch, among the same people; and both marked the commencement of

a new era in their respective spheres."[8]

Lavoisier was born in Paris, and being the son of an opulent

family, was educated under the instruction of the best teachers

of the day. With Lacaille he studied mathematics and astronomy;

with Jussieu, botany; and, finally, chemistry under Rouelle. His

first work of importance was a paper on the practical

illumination of the streets of Paris, for which a prize had been

offered by M. de Sartine, the chief of police. This prize was not

awarded to Lavoisier, but his suggestions were of such importance

that the king directed that a gold medal be bestowed upon the

young author at the public sitting of the Academy in April, 1776.

Two years later, at the age of thirty-five, Lavoisier was

admitted a member of the Academy.

In this same year he began to devote himself almost exclusively

to chemical inquiries, and established a laboratory in his home,

fitted with all manner of costly apparatus and chemicals. Here he

was in constant communication with the great men of science of

Paris, to all of whom his doors were thrown open. One of his

first undertakings in this laboratory was to demonstrate that

water could not be converted into earth by repeated

distillations, as was generally advocated; and to show also that

there was no foundation to the existing belief that it was

possible to convert water into a gas so "elastic" as to pass

through the pores of a vessel. He demonstrated the fallaciousness

of both these theories in 1768-1769 by elaborate experiments, a

single investigation of this series occupying one hundred and one


In 1771 he gave the first blow to the phlogiston theory by his

experiments on the calcination of metals. It will be recalled

that one basis for the belief in phlogiston was the fact that

when a metal was calcined it was converted into an ash, giving up

its "phlogiston" in the process. To restore the metal, it was

necessary to add some substance such as wheat or charcoal to the

ash. Lavoisier, in examining this process of restoration, found

that there was always evolved a great quantity of "air," which he

supposed to be "fixed air" or carbonic acid--the same that

escapes in effervescence of alkalies and calcareous earths, and

in the fermentation of liquors. He then examined the process of

calcination, whereby the phlogiston of the metal was supposed to

have been drawn off. But far from finding that phlogiston or any

other substance had been driven off, he found that something had

been taken on: that the metal "absorbed air," and that the

increased weight of the metal corresponded to the amount of air

"absorbed." Meanwhile he was within grasp of two great

discoveries, that of oxygen and of the composition of the air,

which Priestley made some two years later.

The next important inquiry of this great Frenchman was as to the

composition of diamonds. With the great lens of Tschirnhausen

belonging to the Academy he succeeded in burning up several

diamonds, regardless of expense, which, thanks to his

inheritance, he could ignore. In this process he found that a gas

was given off which precipitated lime from water, and proved to

be carbonic acid. Observing this, and experimenting with other

substances known to give off carbonic acid in the same manner, he

was evidently impressed with the now well-known fact that diamond

and charcoal are chemically the same. But if he did really

believe it, he was cautious in expressing his belief fully. "We

should never have expected," he says, "to find any relation

between charcoal and diamond, and it would be unreasonable to

push this analogy too far; it only exists because both substances

seem to be properly ranged in the class of combustible bodies,

and because they are of all these bodies the most fixed when kept

from contact with air."

As we have seen, Priestley, in 1774, had discovered oxygen, or

"dephlogisticated air." Four years later Lavoisier first

advanced his theory that this element discovered by Priestley was

the universal acidifying or oxygenating principle, which, when

combined with charcoal or carbon, formed carbonic acid; when

combined with sulphur, formed sulphuric (or vitriolic) acid; with

nitrogen, formed nitric acid, etc., and when combined with the

metals formed oxides, or calcides. Furthermore, he postulated the

theory that combustion was not due to any such illusive thing as

"phlogiston," since this did not exist, and it seemed to him that

the phenomena of combustion heretofore attributed to phlogiston

could be explained by the action of the new element oxygen and

heat. This was the final blow to the phlogiston theory, which,

although it had been tottering for some time, had not been

completely overthrown.

In 1787 Lavoisier, in conjunction with Guyon de Morveau,

Berthollet, and Fourcroy, introduced the reform in chemical

nomenclature which until then had remained practically unchanged

since alchemical days. Such expressions as "dephlogisticated" and

"phlogisticated" would obviously have little meaning to a

generation who were no longer to believe in the existence of

phlogiston. It was appropriate that a revolution in chemical

thought should be accompanied by a corresponding revolution in

chemical names, and to Lavoisier belongs chiefly the credit of

bringing about this revolution. In his Elements of Chemistry he

made use of this new nomenclature, and it seemed so clearly an

improvement over the old that the scientific world hastened to

adopt it. In this connection Lavoisier says: "We have,

therefore, laid aside the expression metallic calx altogether,

and have substituted in its place the word oxide. By this it may

be seen that the language we have adopted is both copious and

expressive. The first or lowest degree of oxygenation in bodies

converts them into oxides; a second degree of additional

oxygenation constitutes the class of acids of which the specific

names drawn from their particular bases terminate in ous, as in

the nitrous and the sulphurous acids. The third degree of

oxygenation changes these into the species of acids distinguished

by the termination in ic, as the nitric and sulphuric acids; and,

lastly, we can express a fourth or higher degree of oxygenation

by adding the word oxygenated to the name of the acid, as has

already been done with oxygenated muriatic acid."[9]

This new work when given to the world was not merely an

epoch-making book; it was revolutionary. It not only discarded

phlogiston altogether, but set forth that metals are simple

elements, not compounds of "earth" and "phlogiston." It upheld

Cavendish's demonstration that water itself, like air, is a

compound of oxygen with another element. In short, it was

scientific chemistry, in the modern acceptance of the term.

Lavoisier's observations on combustion are at once important and

interesting: "Combustion," he says, ". . . is the decomposition

of oxygen produced by a combustible body. The oxygen which forms

the base of this gas is absorbed by and enters into combination

with the burning body, while the caloric and light are set free.

Every combustion necessarily supposes oxygenation; whereas, on

the contrary, every oxygenation does not necessarily imply

concomitant combustion; because combustion properly so called

cannot take place without disengagement of caloric and light.

Before combustion can take place, it is necessary that the base

of oxygen gas should have greater affinity to the combustible

body than it has to caloric; and this elective attraction, to use

Bergman's expression, can only take place at a certain degree of

temperature which is different for each combustible substance;

hence the necessity of giving the first motion or beginning to

every combustion by the approach of a heated body. This necessity

of heating any body we mean to burn depends upon certain

considerations which have not hitherto been attended to by any

natural philosopher, for which reason I shall enlarge a little

upon the subject in this place:

"Nature is at present in a state of equilibrium, which cannot

have been attained until all the spontaneous combustions or

oxygenations possible in an ordinary degree of temperature had

taken place.... To illustrate this abstract view of the matter by

example: Let us suppose the usual temperature of the earth a

little changed, and it is raised only to the degree of boiling

water; it is evident that in this case phosphorus, which is

combustible in a considerably lower degree of temperature, would

no longer exist in nature in its pure and simple state, but would

always be procured in its acid or oxygenated state, and its

radical would become one of the substances unknown to chemistry.

By gradually increasing the temperature of the earth, the same

circumstance would successively happen to all the bodies capable

of combustion; and, at the last, every possible combustion having

taken place, there would no longer exist any combustible body

whatever, and every substance susceptible of the operation would

be oxygenated and consequently incombustible.

"There cannot, therefore, exist, as far as relates to us, any

combustible body but such as are non-combustible at the ordinary

temperature of the earth, or, what is the same thing in other

words, that it is essential to the nature of every combustible

body not to possess the property of combustion unless heated, or

raised to a degree of temperature at which its combustion

naturally takes place. When this degree is once produced,

combustion commences, and the caloric which is disengaged by the

decomposition of the oxygen gas keeps up the temperature which is

necessary for continuing combustion. When this is not the

case--that is, when the disengaged caloric is not sufficient for

keeping up the necessary temperature--the combustion ceases. This

circumstance is expressed in the common language by saying that a

body burns ill or with difficulty."[10]

It needed the genius of such a man as Lavoisier to complete the

refutation of the false but firmly grounded phlogiston theory,

and against such a book as his Elements of Chemistry the feeble

weapons of the supporters of the phlogiston theory were hurled in


But while chemists, as a class, had become converts to the new

chemistry before the end of the century, one man, Dr. Priestley,

whose work had done so much to found it, remained unconverted.

In this, as in all his life-work, he showed himself to be a most

remarkable man. Davy said of him, a generation later, that no

other person ever discovered so many new and curious substances

as he; yet to the last he was only an amateur in science, his

profession, as we know, being the ministry. There is hardly

another case in history of a man not a specialist in science

accomplishing so much in original research as did this chemist,

physiologist, electrician; the mathematician, logician, and

moralist; the theologian, mental philosopher, and political

economist. He took all knowledge for his field; but how he found

time for his numberless researches and multifarious writings,

along with his every-day duties, must ever remain a mystery to

ordinary mortals.

That this marvellously receptive, flexible mind should have

refused acceptance to the clearly logical doctrines of the new

chemistry seems equally inexplicable. But so it was. To the

very last, after all his friends had capitulated, Priestley kept

up the fight. From America he sent out his last defy to the

enemy, in 1800, in a brochure entitled "The Doctrine of

Phlogiston Upheld," etc. In the mind of its author it was little

less than a paean of victory; but all the world beside knew that

it was the swan-song of the doctrine of phlogiston. Despite the

defiance of this single warrior the battle was really lost and

won, and as the century closed "antiphlogistic" chemistry had

practical possession of the field.



Small beginnings as have great endings--sometimes. As a case in

point, note what came of the small, original effort of a

self-trained back-country Quaker youth named John Dalton, who

along towards the close of the eighteenth century became

interested in the weather, and was led to construct and use a

crude water-gauge to test the amount of the rainfall. The simple

experiments thus inaugurated led to no fewer than two hundred

thousand recorded observations regarding the weather, which

formed the basis for some of the most epochal discoveries in

meteorology, as we have seen. But this was only a beginning. The

simple rain-gauge pointed the way to the most important

generalization of the nineteenth century in a field of science

with which, to the casual observer, it might seem to have no

alliance whatever. The wonderful theory of atoms, on which the

whole gigantic structure of modern chemistry is founded, was the

logical outgrowth, in the mind of John Dalton, of those early

studies in meteorology.

The way it happened was this: From studying the rainfall, Dalton

turned naturally to the complementary process of evaporation. He

was soon led to believe that vapor exists, in the atmosphere as

an independent gas. But since two bodies cannot occupy the same

space at the same time, this implies that the various atmospheric

gases are really composed of discrete particles. These ultimate

particles are so small that we cannot see them--cannot, indeed,

more than vaguely imagine them--yet each particle of vapor, for

example, is just as much a portion of water as if it were a drop

out of the ocean, or, for that matter, the ocean itself. But,

again, water is a compound substance, for it may be separated, as

Cavendish has shown, into the two elementary substances hydrogen

and oxygen. Hence the atom of water must be composed of two

lesser atoms joined together. Imagine an atom of hydrogen and one

of oxygen. Unite them, and we have an atom of water; sever them,

and the water no longer exists; but whether united or separate

the atoms of hydrogen and of oxygen remain hydrogen and oxygen

and nothing else. Differently mixed together or united, atoms

produce different gross substances; but the elementary atoms

never change their chemical nature--their distinct personality.

It was about the year 1803 that Dalton first gained a full grasp

of the conception of the chemical atom. At once he saw that the

hypothesis, if true, furnished a marvellous key to secrets of

matter hitherto insoluble--questions relating to the relative

proportions of the atoms themselves. It is known, for example,

that a certain bulk of hydrogen gas unites with a certain bulk of

oxygen gas to form water. If it be true that this combination

consists essentially of the union of atoms one with another (each

single atom of hydrogen united to a single atom of oxygen), then

the relative weights of the original masses of hydrogen and of

oxygen must be also the relative weights of each of their

respective atoms. If one pound of hydrogen unites with five and

one-half pounds of oxygen (as, according to Dalton's experiments,

it did), then the weight of the oxygen atom must be five and

one-half times that of the hydrogen atom. Other compounds may

plainly be tested in the same way. Dalton made numerous tests

before he published his theory. He found that hydrogen enters

into compounds in smaller proportions than any other element

known to him, and so, for convenience, determined to take the

weight of the hydrogen atom as unity. The atomic weight of

oxygen then becomes (as given in Dalton's first table of 1803)

5.5; that of water (hydrogen plus oxygen) being of course 6.5.

The atomic weights of about a score of substances are given in

Dalton's first paper, which was read before the Literary and

Philosophical Society of Manchester, October 21, 1803. I wonder

if Dalton himself, great and acute intellect though he had,

suspected, when he read that paper, that he was inaugurating one

of the most fertile movements ever entered on in the whole

history of science?

Be that as it may, it is certain enough that Dalton's

contemporaries were at first little impressed with the novel

atomic theory. Just at this time, as it chanced, a dispute was

waging in the field of chemistry regarding a matter of empirical

fact which must necessarily be settled before such a theory as

that of Dalton could even hope for a bearing. This was the

question whether or not chemical elements unite with one another

always in definite proportions. Berthollet, the great co-worker

with Lavoisier, and now the most authoritative of living

chemists, contended that substances combine in almost

indefinitely graded proportions between fixed extremes. He held

that solution is really a form of chemical combination--a

position which, if accepted, left no room for argument.

But this contention of the master was most actively disputed, in

particular by Louis Joseph Proust, and all chemists of repute

were obliged to take sides with one or the other. For a time the

authority of Berthollet held out against the facts, but at last

accumulated evidence told for Proust and his followers, and

towards the close of the first decade of our century it came to

be generally conceded that chemical elements combine with one

another in fixed and definite proportions.

More than that. As the analysts were led to weigh carefully the

quantities of combining elements, it was observed that the

proportions are not only definite, but that they bear a very

curious relation to one another. If element A combines with two

different proportions of element B to form two compounds, it

appears that the weight of the larger quantity of B is an exact

multiple of that of the smaller quantity. This curious relation

was noticed by Dr. Wollaston, one of the most accurate of

observers, and a little later it was confirmed by Johan Jakob

Berzelius, the great Swedish chemist, who was to be a dominating

influence in the chemical world for a generation to come. But

this combination of elements in numerical proportions was exactly

what Dalton had noticed as early as 1802, and what bad led him

directly to the atomic weights. So the confirmation of this

essential point by chemists of such authority gave the strongest

confirmation to the atomic theory.

During these same years the rising authority of the French

chemical world, Joseph Louis Gay-Lussac, was conducting

experiments with gases, which he had undertaken at first in

conjunction with Humboldt, but which later on were conducted

independently. In 1809, the next year after the publication of

the first volume of Dalton's New System of Chemical Philosophy,

Gay-Lussac published the results of his observations, and among

other things brought out the remarkable fact that gases, under

the same conditions as to temperature and pressure, combine

always in definite numerical proportions as to volume. Exactly

two volumes of hydrogen, for example, combine with one volume of

oxygen to form water. Moreover, the resulting compound gas

always bears a simple relation to the combining volumes. In the

case just cited, the union of two volumes of hydrogen and one of

oxygen results in precisely two volumes of water vapor.

Naturally enough, the champions of the atomic theory seized upon

these observations of Gay-Lussac as lending strong support to

their hypothesis--all of them, that is, but the curiously

self-reliant and self-sufficient author of the atomic theory

himself, who declined to accept the observations of the French

chemist as valid. Yet the observations of Gay-Lussac were

correct, as countless chemists since then have demonstrated anew,

and his theory of combination by volumes became one of the

foundation-stones of the atomic theory, despite the opposition of

the author of that theory.

The true explanation of Gay-Lussac's law of combination by

volumes was thought out almost immediately by an Italian savant,

Amadeo, Avogadro, and expressed in terms of the atomic theory.

The fact must be, said Avogadro, that under similar physical

conditions every form of gas contains exactly the same number of

ultimate particles in a given volume. Each of these ultimate

physical particles may be composed of two or more atoms (as in

the case of water vapor), but such a compound atom conducts

itself as if it were a simple and indivisible atom, as regards

the amount of space that separates it from its fellows under

given conditions of pressure and temperature. The compound atom,

composed of two or more elementary atoms, Avogadro proposed to

distinguish, for purposes of convenience, by the name molecule.

It is to the molecule, considered as the unit of physical

structure, that Avogadro's law applies.

This vastly important distinction between atoms and molecules,

implied in the law just expressed, was published in 1811. Four

years later, the famous French physicist Ampere outlined a

similar theory, and utilized the law in his mathematical

calculations. And with that the law of Avogadro dropped out of

sight for a full generation. Little suspecting that it was the

very key to the inner mysteries of the atoms for which they were

seeking, the chemists of the time cast it aside, and let it fade

from the memory of their science.

This, however, was not strange, for of course the law of Avogadro

is based on the atomic theory, and in 1811 the atomic theory was

itself still being weighed in the balance. The law of multiple

proportions found general acceptance as an empirical fact; but

many of the leading lights of chemistry still looked askance at

Dalton's explanation of this law. Thus Wollaston, though from the

first he inclined to acceptance of the Daltonian view, cautiously

suggested that it would be well to use the non-committal word

"equivalent" instead of "atom"; and Davy, for a similar reason,

in his book of 1812, speaks only of "proportions," binding

himself to no theory as to what might be the nature of these


At least two great chemists of the time, however, adopted the

atomic view with less reservation. One of these was Thomas

Thomson, professor at Edinburgh, who, in 1807, had given an

outline of Dalton's theory in a widely circulated book, which

first brought the theory to the general attention of the chemical

world. The other and even more noted advocate of the atomic

theory was Johan Jakob Berzelius. This great Swedish chemist at

once set to work to put the atomic theory to such tests as might

be applied in the laboratory. He was an analyst of the utmost

skill, and for years be devoted himself to the determination of

the combining weights, "equivalents" or "proportions," of the

different elements. These determinations, in so far as they were

accurately made, were simple expressions of empirical facts,

independent of any theory; but gradually it became more and more

plain that these facts all harmonize with the atomic theory of

Dalton. So by common consent the proportionate combining weights

of the elements came to be known as atomic weights--the name

Dalton had given them from the first--and the tangible conception

of the chemical atom as a body of definite constitution and

weight gained steadily in favor.

From the outset the idea had had the utmost tangibility in the

mind of Dalton. He had all along represented the different atoms

by geometrical symbols--as a circle for oxygen, a circle

enclosing a dot for hydrogen, and the like--and had represented

compounds by placing these symbols of the elements in

juxtaposition. Berzelius proposed to improve upon this method by

substituting for the geometrical symbol the initial of the Latin

name of the element represented--O for oxygen, H for hydrogen,

and so on--a numerical coefficient to follow the letter as an

indication of the number of atoms present in any given compound.

This simple system soon gained general acceptance, and with

slight modifications it is still universally employed. Every

school-boy now is aware that H2O is the chemical way of

expressing the union of two atoms of hydrogen with one of oxygen

to form a molecule of water. But such a formula would have had

no meaning for the wisest chemist before the day of Berzelius.

The universal fame of the great Swedish authority served to give

general currency to his symbols and atomic weights, and the new

point of view thus developed led presently to two important

discoveries which removed the last lingering doubts as to the

validity of the atomic theory. In 1819 two French physicists,

Dulong and Petit, while experimenting with heat, discovered that

the specific heats of solids (that is to say, the amount of heat

required to raise the temperature of a given mass to a given

degree) vary inversely as their atomic weights. In the same year

Eilhard Mitscherlich, a German investigator, observed that

compounds having the same number of atoms to the molecule are

disposed to form the same angles of crystallization--a property

which he called isomorphism.

Here, then, were two utterly novel and independent sets of

empirical facts which harmonize strangely with the supposition

that substances are composed of chemical atoms of a determinate

weight. This surely could not be coincidence--it tells of law.

And so as soon as the claims of Dulong and Petit and of

Mitscherlich had been substantiated by other observers, the laws

of the specific heat of atoms, and of isomorphism, took their

place as new levers of chemical science. With the aid of these

new tools an impregnable breastwork of facts was soon piled about

the atomic theory. And John Dalton, the author of that theory,

plain, provincial Quaker, working on to the end in

semi-retirement, became known to all the world and for all time

as a master of masters.


During those early years of the nineteenth century, when Dalton

was grinding away at chemical fact and theory in his obscure

Manchester laboratory, another Englishman held the attention of

the chemical world with a series of the most brilliant and widely

heralded researches. This was Humphry Davy, a young man who had

conic to London in 1801, at the instance of Count Rumford, to

assume the chair of chemical philosophy in the Royal Institution,

which the famous American had just founded.

Here, under Davy's direction, the largest voltaic battery yet

constructed had been put in operation, and with its aid the

brilliant young experimenter was expected almost to perform

miracles. And indeed he scarcely disappointed the expectation,

for with the aid of his battery he transformed so familiar a

substance as common potash into a metal which was not only so

light that it floated on water, but possessed the seemingly

miraculous property of bursting into flames as soon as it came in

contact with that fire-quenching liquid. If this were not a

miracle, it had for the popular eye all the appearance of the


What Davy really had done was to decompose the potash, which

hitherto had been supposed to be elementary, liberating its

oxygen, and thus isolating its metallic base, which he named

potassium. The same thing was done with soda, and the closely

similar metal sodium was discovered--metals of a unique type,

possessed of a strange avidity for oxygen, and capable of seizing

on it even when it is bound up in the molecules of water.

Considered as mere curiosities, these discoveries were

interesting, but aside from that they were of great theoretical

importance, because they showed the compound nature of some

familiar chemicals that had been regarded as elements. Several

other elementary earths met the same fate when subjected to the

electrical influence; the metals barium, calcium, and strontium

being thus discovered. Thereafter Davy always referred to the

supposed elementary substances (including oxygen, hydrogen, and

the rest) as "unde-compounded" bodies. These resist all present

efforts to decompose them, but how can one know what might not

happen were they subjected to an influence, perhaps some day to

be discovered, which exceeds the battery in power as the battery

exceeds the blowpipe?

Another and even more important theoretical result that flowed

from Davy's experiments during this first decade of the century

was the proof that no elementary substances other than hydrogen

and oxygen are produced when pure water is decomposed by the

electric current. It was early noticed by Davy and others that

when a strong current is passed through water, alkalies appear at

one pole of the battery and acids at the other, and this though

the water used were absolutely pure. This seemingly told of the

creation of elements--a transmutation but one step removed from

the creation of matter itself--under the influence of the new

"force." It was one of Davy's greatest triumphs to prove, in the

series of experiments recorded in his famous Bakerian lecture of

1806, that the alleged creation of elements did not take place,

the substances found at the poles of the battery having been

dissolved from the walls of the vessels in which the water

experimented upon had been placed. Thus the same implement which

had served to give a certain philosophical warrant to the fading

dreams of alchemy banished those dreams peremptorily from the

domain of present science.

"As early as 1800," writes Davy, "I had found that when separate

portions of distilled water, filling two glass tubes, connected

by moist bladders, or any moist animal or vegetable substances,

were submitted to the electrical action of the pile of Volta by

means of gold wires, a nitro-muriatic solution of gold appeared

in the tube containing the positive wire, or the wire

transmitting the electricity, and a solution of soda in the

opposite tube; but I soon ascertained that the muriatic acid owed

its existence to the animal or vegetable matters employed; for

when the same fibres of cotton were made use of in successive

experiments, and washed after every process in a weak solution of

nitric acid, the water in the apparatus containing them, though

acted on for a great length of time with a very strong power, at

last produced no effects upon nitrate of silver.

"In cases when I had procured much soda, the glass at its point

of contact with the wire seemed considerably corroded; and I was

confirmed in my idea of referring the production of the alkali

principally to this source, by finding that no fixed saline

matter could be obtained by electrifying distilled water in a

single agate cup from two points of platina with the Voltaic


"Mr. Sylvester, however, in a paper published in Mr. Nicholson's

journal for last August, states that though no fixed alkali or

muriatic acid appears when a single vessel is employed, yet that

they are both formed when two vessels are used. And to do away

with all objections with regard to vegetable substances or glass,

he conducted his process in a vessel made of baked tobacco-pipe

clay inserted in a crucible of platina. I have no doubt of the

correctness of his results; but the conclusion appears

objectionable. He conceives, that he obtained fixed alkali,

because the fluid after being heated and evaporated left a matter

that tinged turmeric brown, which would have happened had it been

lime, a substance that exists in considerable quantities in all

pipe-clay; and even allowing the presence of fixed alkali, the

materials employed for the manufacture of tobacco-pipes are not

at all such as to exclude the combinations of this substance.

"I resumed the inquiry; I procured small cylindrical cups of

agate of the capacity of about one-quarter of a cubic inch each.

They were boiled for some hours in distilled water, and a piece

of very white and transparent amianthus that had been treated in

the same way was made then to connect together; they were filled

with distilled water and exposed by means of two platina wires to

a current of electricity, from one hundred and fifty pairs of

plates of copper and zinc four inches square, made active by

means of solution of alum. After forty-eight hours the process

was examined: Paper tinged with litmus plunged into the tube

containing the transmitting or positive wire was immediately

strongly reddened. Paper colored by turmeric introduced into the

other tube had its color much deepened; the acid matter gave a

very slight degree of turgidness to solution of nitrate of soda.

The fluid that affected turmeric retained this property after

being strongly boiled; and it appeared more vivid as the quantity

became reduced by evaporation; carbonate of ammonia was mixed

with it, and the whole dried and exposed to a strong heat; a

minute quantity of white matter remained, which, as far as my

examinations could go, had the properties of carbonate of soda. I

compared it with similar minute portions of the pure carbonates

of potash, and similar minute portions of the pure carbonates of

potash and soda. It was not so deliquescent as the former of

these bodies, and it formed a salt with nitric acid, which, like

nitrate of soda, soon attracted moisture from a damp atmosphere

and became fluid.

"This result was unexpected, but it was far from convincing me

that the substances which were obtained were generated. In a

similar process with glass tubes, carried on under exactly the

same circumstances and for the same time, I obtained a quantity

of alkali which must have been more than twenty times greater,

but no traces of muriatic acid. There was much probability that

the agate contained some minute portion of saline matter, not

easily detected by chemical analysis, either in combination or

intimate cohesion in its pores. To determine this, I repeated

this a second, a third, and a fourth time. In the second

experiment turbidness was still produced by a solution of nitrate

of silver in the tube containing the acid, but it was less

distinct; in the third process it was barely perceptible; and in

the fourth process the two fluids remained perfectly clear after

the mixture. The quantity of alkaline matter diminished in every

operation; and in the last process, though the battery had been

kept in great activity for three days, the fluid possessed, in a

very slight degree, only the power of acting on paper tinged with

turmeric; but its alkaline property was very sensible to litmus

paper slightly reddened, which is a much more delicate test; and

after evaporation and the process by carbonate of ammonia, a

barely perceptible quantity of fixed alkali was still left. The

acid matter in the other tube was abundant; its taste was sour;

it smelled like water over which large quantities of nitrous gas

have been long kept; it did not effect solution of muriate of

barytes; and a drop of it placed upon a polished plate of silver

left, after evaporation, a black stain, precisely similar to that

produced by extremely diluted nitrous acid.

"After these results I could no longer doubt that some saline

matter existing in the agate tubes had been the source of the

acid matter capable of precipitating nitrate of silver and much

of the alkali. Four additional repetitions of the process,

however, convinced me that there was likewise some other cause

for the presence of this last substance; for it continued to

appear to the last in quantities sufficiently distinguishable,

and apparently equal in every case. I had used every precaution,

I had included the tube in glass vessels out of the reach of the

circulating air; all the acting materials had been repeatedly

washed with distilled water; and no part of them in contact with

the fluid had been touched by the fingers.

"The only substance that I could now conceive as furnishing the

fixed alkali was the water itself. This water appeared pure by

the tests of nitrate of silver and muriate of barytes; but potash

of soda, as is well known, rises in small quantities in rapid

distillation; and the New River water which I made use of

contains animal and vegetable impurities, which it was easy to

conceive might furnish neutral salts capable of being carried

over in vivid ebullition."[1] Further experiment proved the

correctness of this inference, and the last doubt as to the

origin of the puzzling chemical was dispelled.

Though the presence of the alkalies and acids in the water was

explained, however, their respective migrations to the negative

and positive poles of the battery remained to be accounted for.

Davy's classical explanation assumed that different elements

differ among themselves as to their electrical properties, some

being positively, others negatively, electrified. Electricity

and "chemical affinity," he said, apparently are manifestations

of the same force, acting in the one case on masses, in the other

on particles. Electro-positive particles unite with

electro-negative particles to form chemical compounds, in virtue

of the familiar principle that opposite electricities attract one

another. When compounds are decomposed by the battery, this

mutual attraction is overcome by the stronger attraction of the

poles of the battery itself.

This theory of binary composition of all chemical compounds,

through the union of electro-positive and electro-negative atoms

or molecules, was extended by Berzelius, and made the basis of

his famous system of theoretical chemistry. This theory held

that all inorganic compounds, however complex their composition,

are essentially composed of such binary combinations. For many

years this view enjoyed almost undisputed sway. It received what

seemed strong confirmation when Faraday showed the definite

connection between the amount of electricity employed and the

amount of decomposition produced in the so-called electrolyte.

But its claims were really much too comprehensive, as subsequent

discoveries proved.


When Berzelius first promulgated his binary theory he was careful

to restrict its unmodified application to the compounds of the

inorganic world. At that time, and for a long time thereafter,

it was supposed that substances of organic nature had some

properties that kept them aloof from the domain of inorganic

chemistry. It was little doubted that a so-called "vital force"

operated here, replacing or modifying the action of ordinary

"chemical affinity." It was, indeed, admitted that organic

compounds are composed of familiar elements--chiefly carbon,

oxygen, hydrogen, and nitrogen; but these elements were supposed

to be united in ways that could not be imitated in the domain of

the non-living. It was regarded almost as an axiom of chemistry

that no organic compound whatever could be put together from its

elements--synthesized--in the laboratory. To effect the synthesis

of even the simplest organic compound, it was thought that the

"vital force" must be in operation.

Therefore a veritable sensation was created in the chemical world

when, in the year 1828, it was announced that the young German

chemist, Friedrich Wohler, formerly pupil of Berzelius, and

already known as a coming master, had actually synthesized the

well-known organic product urea in his laboratory at Sacrow. The

"exception which proves the rule" is something never heard of in

the domain of logical science. Natural law knows no exceptions.

So the synthesis of a single organic compound sufficed at a blow

to break down the chemical barrier which the imagination of the

fathers of the science had erected between animate and inanimate

nature. Thenceforth the philosophical chemist would regard the

plant and animal organisms as chemical laboratories in which

conditions are peculiarly favorable for building up complex

compounds of a few familiar elements, under the operation of

universal chemical laws. The chimera "vital force" could no

longer gain recognition in the domain of chemistry.

Now a wave of interest in organic chemistry swept over the

chemical world, and soon the study of carbon compounds became as

much the fashion as electrochemistry had been in the, preceding


Foremost among the workers who rendered this epoch of organic

chemistry memorable were Justus Liebig in Germany and Jean

Baptiste Andre Dumas in France, and their respective pupils,

Charles Frederic Gerhardt and Augustus Laurent. Wohler, too,

must be named in the same breath, as also must Louis Pasteur,

who, though somewhat younger than the others, came upon the scene

in time to take chief part in the most important of the

controversies that grew out of their labors.

Several years earlier than this the way had been paved for the

study of organic substances by Gay-Lussac's discovery, made in

1815, that a certain compound of carbon and nitrogen, which he

named cyanogen, has a peculiar degree of stability which enables

it to retain its identity and enter into chemical relations after

the manner of a simple body. A year later Ampere discovered that

nitrogen and hydrogen, when combined in certain proportions to

form what he called ammonium, have the same property. Berzelius

had seized upon this discovery of the compound radical, as it was

called, because it seemed to lend aid to his dualistic theory. He

conceived the idea that all organic compounds are binary unions

of various compound radicals with an atom of oxygen, announcing

this theory in 1818. Ten years later, Liebig and Wohler undertook

a joint investigation which resulted in proving that compound

radicals are indeed very abundant among organic substances. Thus

the theory of Berzelius seemed to be substantiated, and organic

chemistry came to be defined as the chemistry of compound


But even in the day of its seeming triumph the dualistic theory

was destined to receive a rude shock. This came about through

the investigations of Dumas, who proved that in a certain organic

substance an atom of hydrogen may be removed and an atom of

chlorine substituted in its place without destroying the

integrity of the original compound--much as a child might

substitute one block for another in its play-house. Such a

substitution would be quite consistent with the dualistic theory,

were it not for the very essential fact that hydrogen is a

powerfully electro-positive element, while chlorine is as

strongly electro-negative. Hence the compound radical which

united successively with these two elements must itself be at one

time electro-positive, at another electro-negative--a seeming

inconsistency which threw the entire Berzelian theory into


In its place there was elaborated, chiefly through the efforts of

Laurent and Gerhardt, a conception of the molecule as a unitary

structure, built up through the aggregation of various atoms, in

accordance with "elective affinities" whose nature is not yet

understood A doctrine of "nuclei" and a doctrine of "types" of

molecular structure were much exploited, and, like the doctrine

of compound radicals, became useful as aids to memory and guides

for the analyst, indicating some of the plans of molecular

construction, though by no means penetrating the mysteries of

chemical affinity. They are classifications rather than

explanations of chemical unions. But at least they served an

important purpose in giving definiteness to the idea of a

molecular structure built of atoms as the basis of all

substances. Now at last the word molecule came to have a distinct

meaning, as distinct from "atom," in the minds of the generality

of chemists, as it had had for Avogadro a third of a century

before. Avogadro's hypothesis that there are equal numbers of

these molecules in equal volumes of gases, under fixed

conditions, was revived by Gerhardt, and a little later, under

the championship of Cannizzaro, was exalted to the plane of a

fixed law. Thenceforth the conception of the molecule was to be

as dominant a thought in chemistry as the idea of the atom had

become in a previous epoch.


Of course the atom itself was in no sense displaced, but

Avogadro's law soon made it plain that the atom had often usurped

territory that did not really belong to it. In many cases the

chemists had supposed themselves dealing with atoms as units

where the true unit was the molecule. In the case of elementary

gases, such as hydrogen and oxygen, for example, the law of equal

numbers of molecules in equal spaces made it clear that the atoms

do not exist isolated, as had been supposed. Since two volumes

of hydrogen unite with one volume of oxygen to form two volumes

of water vapor, the simplest mathematics show, in the light of

Avogadro's law, not only that each molecule of water must contain

two hydrogen atoms (a point previously in dispute), but that the

original molecules of hydrogen and oxygen must have been composed

in each case of two atoms---else how could one volume of oxygen

supply an atom for every molecule of two volumes of water?

What, then, does this imply? Why, that the elementary atom has

an avidity for other atoms, a longing for companionship, an

"affinity"--call it what you will--which is bound to be satisfied

if other atoms are in the neighborhood. Placed solely among

atoms of its own kind, the oxygen atom seizes on a fellow oxygen

atom, and in all their mad dancings these two mates cling

together--possibly revolving about each other in miniature

planetary orbits. Precisely the same thing occurs among the

hydrogen atoms. But now suppose the various pairs of oxygen atoms

come near other pairs of hydrogen atoms (under proper conditions

which need not detain us here), then each oxygen atom loses its

attachment for its fellow, and flings itself madly into the

circuit of one of the hydrogen couplets, and--presto!--there are

only two molecules for every three there were before, and free

oxygen and hydrogen have become water. The whole process, stated

in chemical phraseology, is summed up in the statement that under

the given conditions the oxygen atoms had a greater affinity for

the hydrogen atoms than for one another.

As chemists studied the actions of various kinds of atoms, in

regard to their unions with one another to form molecules, it

gradually dawned upon them that not all elements are satisfied

with the same number of companions. Some elements ask only one,

and refuse to take more; while others link themselves, when

occasion offers, with two, three, four, or more. Thus we saw that

oxygen forsook a single atom of its own kind and linked itself

with two atoms of hydrogen. Clearly, then, the oxygen atom, like

a creature with two hands, is able to clutch two other atoms.

But we have no proof that under any circumstances it could hold

more than two. Its affinities seem satisfied when it has two

bonds. But, on the other hand, the atom of nitrogen is able to

hold three atoms of hydrogen, and does so in the molecule of

ammonium (NH3); while the carbon atom can hold four atoms of

hydrogen or two atoms of oxygen.

Evidently, then, one atom is not always equivalent to another

atom of a different kind in combining powers. A recognition of

this fact by Frankland about 1852, and its further investigation

by others (notably A. Kekule and A. S. Couper), led to the

introduction of the word equivalent into chemical terminology in

a new sense, and in particular to an understanding of the

affinities or "valency" of different elements, which proved of

the most fundamental importance. Thus it was shown that, of the

four elements that enter most prominently into organic compounds,

hydrogen can link itself with only a single bond to any other

element--it has, so to speak, but a single hand with which to

grasp--while oxygen has capacity for two bonds, nitrogen for

three (possibly for five), and carbon for four. The words

monovalent, divalent, trivalent, tretrava-lent, etc., were coined

to express this most important fact, and the various elements

came to be known as monads, diads, triads, etc. Just why

different elements should differ thus in valency no one as yet

knows; it is an empirical fact that they do. And once the nature

of any element has been determined as regards its valency, a most

important insight into the possible behavior of that element has

been secured. Thus a consideration of the fact that hydrogen is

monovalent, while oxygen is divalent, makes it plain that we must

expect to find no more than three compounds of these two

elements--namely, H--O--(written HO by the chemist, and called

hydroxyl); H--O--H (H2O, or water), and H--O--O--H (H2O2, or

hydrogen peroxide). It will be observed that in the first of

these compounds the atom of oxygen stands, so to speak, with one

of its hands free, eagerly reaching out, therefore, for another

companion, and hence, in the language of chemistry, forming an

unstable compound. Again, in the third compound, though all hands

are clasped, yet one pair links oxygen with oxygen; and this also

must be an unstable union, since the avidity of an atom for its

own kind is relatively weak. Thus the well-known properties of

hydrogen peroxide are explained, its easy decomposition, and the

eagerness with which it seizes upon the elements of other


But the molecule of water, on the other hand, has its atoms

arranged in a state of stable equilibrium, all their affinities

being satisfied. Each hydrogen atom has satisfied its own

affinity by clutching the oxygen atom; and the oxygen atom has

both its bonds satisfied by clutching back at the two hydrogen

atoms. Therefore the trio, linked in this close bond, have no

tendency to reach out for any other companion, nor, indeed, any

power to hold another should it thrust itself upon them. They

form a "stable" compound, which under all ordinary circumstances

will retain its identity as a molecule of water, even though the

physical mass of which it is a part changes its condition from a

solid to a gas from ice to vapor.

But a consideration of this condition of stable equilibrium in

the molecule at once suggests a new question: How can an

aggregation of atoms, having all their affinities satisfied, take

any further part in chemical reactions? Seemingly such a

molecule, whatever its physical properties, must be chemically

inert, incapable of any atomic readjustments. And so in point of

fact it is, so long as its component atoms cling to one another

unremittingly. But this, it appears, is precisely what the atoms

are little prone to do. It seems that they are fickle to the last

degree in their individual attachments, and are as prone to break

away from bondage as they are to enter into it. Thus the oxygen

atom which has just flung itself into the circuit of two hydrogen

atoms, the next moment flings itself free again and seeks new

companions. It is for all the world like the incessant change of

partners in a rollicking dance. This incessant dissolution and

reformation of molecules in a substance which as a whole remains

apparently unchanged was first fully appreciated by Ste.-Claire

Deville, and by him named dissociation. It is a process which

goes on much more actively in some compounds than in others, and

very much more actively under some physical conditions (such as

increase of temperature) than under others. But apparently no

substances at ordinary temperatures, and no temperature above the

absolute zero, are absolutely free from its disturbing influence.

Hence it is that molecules having all the valency of their atoms

fully satisfied do not lose their chemical activity--since each

atom is momentarily free in the exchange of partners, and may

seize upon different atoms from its former partners, if those it

prefers are at hand.

While, however, an appreciation of this ceaseless activity of the

atom is essential to a proper understanding of its chemical

efficiency, yet from another point of view the "saturated"

molecule--that is, the molecule whose atoms have their valency

all satisfied--may be thought of as a relatively fixed or stable

organism. Even though it may presently be torn down, it is for

the time being a completed structure; and a consideration of the

valency of its atoms gives the best clew that has hitherto been

obtainable as to the character of its architecture. How

important this matter of architecture of the molecule--of space

relations of the atoms--may be was demonstrated as long ago as

1823, when Liebig and Wohler proved, to the utter bewilderment of

the chemical world, that two substances may have precisely the

same chemical constitution--the same number and kind of

atoms--and yet differ utterly in physical properties. The word

isomerism was coined by Berzelius to express this anomalous

condition of things, which seemed to negative the most

fundamental truths of chemistry. Naming the condition by no

means explained it, but the fact was made clear that something

besides the mere number and kind of atoms is important in the

architecture of a molecule. It became certain that atoms are not

thrown together haphazard to build a molecule, any more than

bricks are thrown together at random to form a house.

How delicate may be the gradations of architectural design in

building a molecule was well illustrated about 1850, when Pasteur

discovered that some carbon compounds--as certain sugars--can

only be distinguished from one another, when in solution, by the

fact of their twisting or polarizing a ray of light to the left

or to the right, respectively. But no inkling of an explanation

of these strange variations of molecular structure came until the

discovery of the law of valency. Then much of the mystery was

cleared away; for it was plain that since each atom in a molecule

can hold to itself only a fixed number of other atoms, complex

molecules must have their atoms linked in definite chains or

groups. And it is equally plain that where the atoms are

numerous, the exact plan of grouping may sometimes be susceptible

of change without doing violence to the law of valency. It is in

such cases that isomerism is observed to occur.

By paying constant heed to this matter of the affinities,

chemists are able to make diagrammatic pictures of the plan of

architecture of any molecule whose composition is known. In the

simple molecule of water (H2O), for example, the two hydrogen

atoms must have released each other before they could join the

oxygen, and the manner of linking must apparently be that

represented in the graphic formula H--O--H. With molecules

composed of a large number of atoms, such graphic representation

of the scheme of linking is of course increasingly difficult,

yet, with the affinities for a guide, it is always possible. Of

course no one supposes that such a formula, written in a single

plane, can possibly represent the true architecture of the

molecule: it is at best suggestive or diagrammatic rather than

pictorial. Nevertheless, it affords hints as to the structure of

the molecule such as the fathers of chemistry would not have

thought it possible ever to attain.


These utterly novel studies of molecular architecture may seem at

first sight to take from the atom much of its former prestige as

the all-important personage of the chemical world. Since so much

depends upon the mere position of the atoms, it may appear that

comparatively little depends upon the nature of the atoms

themselves. But such a view is incorrect, for on closer

consideration it will appear that at no time has the atom been

seen to renounce its peculiar personality. Within certain limits

the character of a molecule may be altered by changing the

positions of its atoms (just as different buildings may be

constructed of the same bricks), but these limits are sharply

defined, and it would be as impossible to exceed them as it would

be to build a stone building with bricks. From first to last the

brick remains a brick, whatever the style of architecture it

helps to construct; it never becomes a stone. And just as closely

does each atom retain its own peculiar properties, regardless of

its surroundings.

Thus, for example, the carbon atom may take part in the formation

at one time of a diamond, again of a piece of coal, and yet again

of a particle of sugar, of wood fibre, of animal tissue, or of a

gas in the atmosphere; but from first to last--from glass-cutting

gem to intangible gas--there is no demonstrable change whatever

in any single property of the atom itself. So far as we know, its

size, its weight, its capacity for vibration or rotation, and its

inherent affinities, remain absolutely unchanged throughout all

these varying fortunes of position and association. And the same

thing is true of every atom of all of the seventy-odd elementary

substances with which the modern chemist is acquainted. Every one

appears always to maintain its unique integrity, gaining nothing

and losing nothing.

All this being true, it would seem as if the position of the

Daltonian atom as a primordial bit of matter, indestructible and

non-transmutable, had been put to the test by the chemistry of

our century, and not found wanting. Since those early days of the

century when the electric battery performed its miracles and

seemingly reached its limitations in the hands of Davy, many new

elementary substances have been discovered, but no single element

has been displaced from its position as an undecomposable body.

Rather have the analyses of the chemist seemed to make it more

and more certain that all elementary atoms are in truth what John

Herschel called them, "manufactured articles"--primordial,

changeless, indestructible.

And yet, oddly enough, it has chanced that hand in hand with the

experiments leading to such a goal have gone other experiments

arid speculations of exactly the opposite tenor. In each

generation there have been chemists among the leaders of their

science who have refused to admit that the so-called elements are

really elements at all in any final sense, and who have sought

eagerly for proof which might warrant their scepticism. The first

bit of evidence tending to support this view was furnished by an

English physician, Dr. William Prout, who in 1815 called

attention to a curious relation to be observed between the atomic

weight of the various elements. Accepting the figures given by

the authorities of the time (notably Thomson and Berzelius), it

appeared that a strikingly large proportion of the atomic weights

were exact multiples of the weight of hydrogen, and that others

differed so slightly that errors of observation might explain the

discrepancy. Prout felt that it could not be accidental, and he

could think of no tenable explanation, unless it be that the

atoms of the various alleged elements are made up of different

fixed numbers of hydrogen atoms. Could it be that the one true

element--the one primal matter--is hydrogen, and that all other

forms of matter are but compounds of this original substance?

Prout advanced this startling idea at first tentatively, in an

anonymous publication; but afterwards he espoused it openly and

urged its tenability. Coming just after Davy's dissociation of

some supposed elements, the idea proved alluring, and for a time

gained such popularity that chemists were disposed to round out

the observed atomic weights of all elements into whole numbers.

But presently renewed determinations of the atomic weights seemed

to discountenance this practice, and Prout's alleged law fell

into disrepute. It was revived, however, about 1840, by Dumas,

whose great authority secured it a respectful hearing, and whose

careful redetermination of the weight of carbon, making it

exactly twelve times that of hydrogen, aided the cause.

Subsequently Stas, the pupil of Dumas, undertook a long series of

determinations of atomic weights, with the expectation of

confirming the Proutian hypothesis. But his results seemed to

disprove the hypothesis, for the atomic weights of many elements

differed from whole numbers by more, it was thought, than the

limits of error of the experiments. It was noteworthy, however,

that the confidence of Dumas was not shaken, though he was led to

modify the hypothesis, and, in accordance with previous

suggestions of Clark and of Marignac, to recognize as the

primordial element, not hydrogen itself, but an atom half the

weight, or even one-fourth the weight, of that of hydrogen, of

which primordial atom the hydrogen atom itself is compounded. But

even in this modified form the hypothesis found great opposition

from experimental observers.

In 1864, however, a novel relation between the weights of the

elements and their other characteristics was called to the

attention of chemists by Professor John A. R. Newlands, of

London, who had noticed that if the elements are arranged

serially in the numerical order of their atomic weights, there is

a curious recurrence of similar properties at intervals of eight

elements This so-called "law of octaves" attracted little

immediate attention, but the facts it connotes soon came under

the observation of other chemists, notably of Professors Gustav

Hinrichs in America, Dmitri Mendeleeff in Russia, and Lothar

Meyer in Germany. Mendeleeff gave the discovery fullest

expression, explicating it in 1869, under the title of "the

periodic law."

Though this early exposition of what has since been admitted to

be a most important discovery was very fully outlined, the

generality of chemists gave it little heed till a decade or so

later, when three new elements, gallium, scandium, and germanium,

were discovered, which, on being analyzed, were quite

unexpectedly found to fit into three gaps which Mendeleeff had

left in his periodic scale. In effect the periodic law had

enabled Mendeleeff to predicate the existence of the new elements

years before they were discovered. Surely a system that leads to

such results is no mere vagary. So very soon the periodic law

took its place as one of the most important generalizations of

chemical science.

This law of periodicity was put forward as an expression of

observed relations independent of hypothesis; but of course the

theoretical bearings of these facts could not be overlooked. As

Professor J. H. Gladstone has said, it forces upon us "the

conviction that the elements are not separate bodies created

without reference to one another, but that they have been

originally fashioned, or have been built up, from one another,

according to some general plan." It is but a short step from

that proposition to the Proutian hypothesis.


But the atomic weights are not alone in suggesting the compound

nature of the alleged elements. Evidence of a totally different

kind has contributed to the same end, from a source that could

hardly have been imagined when the Proutian hypothesis, was

formulated, through the tradition of a novel weapon to the

armamentarium of the chemist--the spectroscope. The perfection

of this instrument, in the hands of two German scientists, Gustav

Robert Kirchhoff and Robert Wilhelm Bunsen, came about through

the investigation, towards the middle of the century, of the

meaning of the dark lines which had been observed in the solar

spectrum by Fraunhofer as early as 1815, and by Wollaston a

decade earlier. It was suspected by Stokes and by Fox Talbot in

England, but first brought to demonstration by Kirchhoff and

Bunsen, that these lines, which were known to occupy definite

positions in the spectrum, are really indicative of particular

elementary substances. By means of the spectroscope, which is

essentially a magnifying lens attached to a prism of glass, it is

possible to locate the lines with great accuracy, and it was soon

shown that here was a new means of chemical analysis of the most

exquisite delicacy. It was found, for example, that the

spectroscope could detect the presence of a quantity of sodium so

infinitesimal as the one two-hundred-thousandth of a grain. But

what was even more important, the spectroscope put no limit upon

the distance of location of the substance it tested, provided

only that sufficient light came from it. The experiments it

recorded might be performed in the sun, or in the most distant

stars or nebulae; indeed, one of the earliest feats of the

instrument was to wrench from the sun the secret of his chemical


To render the utility of the spectroscope complete, however, it

was necessary to link with it another new chemical

agency--namely, photography. This now familiar process is based

on the property of light to decompose certain unstable compounds

of silver, and thus alter their chemical composition. Davy and

Wedgwood barely escaped the discovery of the value of the

photographic method early in the nineteenth century. Their

successors quite overlooked it until about 1826, when Louis J. M.

Daguerre, the French chemist, took the matter in hand, and after

many years of experimentation brought it to relative perfection

in 1839, in which year the famous daguerreotype first brought the

matter to popular attention. In the same year Mr. Fox Talbot read

a paper on the subject before the Royal Society, and soon

afterwards the efforts of Herschel and numerous other natural

philosophers contributed to the advancement of the new method.

In 1843 Dr. John W. Draper, the famous English-American chemist

and physiologist, showed that by photography the Fraunhofer lines

in the solar spectrum might be mapped with absolute accuracy;

also proving that the silvered film revealed many lines invisible

to the unaided eye. The value of this method of observation was

recognized at once, and, as soon as the spectroscope was

perfected, the photographic method, in conjunction with its use,

became invaluable to the chemist. By this means comparisons of

spectra may be made with a degree of accuracy not otherwise

obtainable; and, in case of the stars, whole clusters of spectra

may be placed on record at a single observation.

As the examination of the sun and stars proceeded, chemists were

amazed or delighted, according to their various preconceptions,

to witness the proof that many familiar terrestrial elements are

to be found in the celestial bodies. But what perhaps surprised

them most was to observe the enormous preponderance in the

sidereal bodies of the element hydrogen. Not only are there vast

quantities of this element in the sun's atmosphere, but some

other suns appeared to show hydrogen lines almost exclusively in

their spectra. Presently it appeared that the stars of which

this is true are those white stars, such as Sirius, which had

been conjectured to be the hottest; whereas stars that are only

red-hot, like our sun, show also the vapors of many other

elements, including iron and other metals.

In 1878 Professor J. Norman Lockyer, in a paper before the Royal

Society, called attention to the possible significance of this

series of observations. He urged that the fact of the sun showing

fewer elements than are observed here on the cool earth, while

stars much hotter than the sun show chiefly one element, and that

one hydrogen, the lightest of known elements, seemed to give

color to the possibility that our alleged elements are really

compounds, which at the temperature of the hottest stars may be

decomposed into hydrogen, the latter "element" itself being also

doubtless a compound, which might be resolved under yet more

trying conditions.

Here, then, was what might be termed direct experimental evidence

for the hypothesis of Prout. Unfortunately, however, it is

evidence of a kind which only a few experts are competent to

discuss--so very delicate a matter is the spectral analysis of

the stars. What is still more unfortunate, the experts do not

agree among themselves as to the validity of Professor Lockyer's

conclusions. Some, like Professor Crookes, have accepted them

with acclaim, hailing Lockyer as "the Darwin of the inorganic

world," while others have sought a different explanation of the

facts he brings forward. As yet it cannot be said that the

controversy has been brought to final settlement. Still, it is

hardly to be doubted that now, since the periodic law has seemed

to join hands with the spectroscope, a belief in the compound

nature of the so-called elements is rapidly gaining ground among

chemists. More and more general becomes the belief that the

Daltonian atom is really a compound radical, and that back of the

seeming diversity of the alleged elements is a single form of

primordial matter. Indeed, in very recent months, direct

experimental evidence for this view has at last come to hand,

through the study of radio-active substances. In a later chapter

we shall have occasion to inquire how this came about.



An epoch in physiology was made in the eighteenth century by the

genius and efforts of Albrecht von Haller (1708-1777), of Berne,

who is perhaps as worthy of the title "The Great" as any

philosopher who has been so christened by his contemporaries

since the time of Hippocrates. Celebrated as a physician, he was

proficient in various fields, being equally famed in his own time

as poet, botanist, and statesman, and dividing his attention

between art and science.

As a child Haller was so sickly that he was unable to amuse

himself with the sports and games common to boys of his age, and

so passed most of his time poring over books. When ten years of

age he began writing poems in Latin and German, and at fifteen

entered the University of Tubingen. At seventeen he wrote

learned articles in opposition to certain accepted doctrines, and

at nineteen he received his degree of doctor. Soon after this he

visited England, where his zeal in dissecting brought him under

suspicion of grave-robbery, which suspicion made it expedient for

him to return to the Continent. After studying botany in Basel

for some time he made an extended botanical journey through

Switzerland, finally settling in his native city, Berne, as a

practising physician. During this time he did not neglect either

poetry or botany, publishing anonymously a collection of poems.

In 1736 he was called to Gottingen as professor of anatomy,

surgery, chemistry, and botany. During his labors in the

university he never neglected his literary work, sometimes living

and sleeping for days and nights together in his library, eating

his meals while delving in his books, and sleeping only when

actually compelled to do so by fatigue. During all this time he

was in correspondence with savants from all over the world, and

it is said of him that he never left a letter of any kind


Haller's greatest contribution to medical science was his famous

doctrine of irritability, which has given him the name of "father

of modern nervous physiology," just as Harvey is called "the

father of the modern physiology of the blood." It has been said

of this famous doctrine of irritability that "it moved all the

minds of the century--and not in the departments of medicine

alone--in a way of which we of the present day have no

satisfactory conception, unless we compare it with our modern


The principle of general irritability had been laid down by

Francis Glisson (1597-1677) from deductive studies, but Haller

proved by experiments along the line of inductive methods that

this irritability was not common to all "fibre as well as to the

fluids of the body," but something entirely special, and peculiar

only to muscular substance. He distinguished between irritability

of muscles and sensibility of nerves. In 1747 he gave as the

three forces that produce muscular movements: elasticity, or

"dead nervous force"; irritability, or "innate nervous force";

and nervous force in itself. And in 1752 he described one

hundred and ninety experiments for determining what parts of the

body possess "irritability"--that is, the property of contracting

when stimulated. His conclusion that this irritability exists in

muscular substance alone and is quite independent of the nerves

proceeding to it aroused a controversy that was never definitely

settled until late in the nineteenth century, when Haller's

theory was found to be entirely correct.

It was in pursuit of experiments to establish his theory of

irritability that Haller made his chief discoveries in embryology

and development. He proved that in the process of incubation of

the egg the first trace of the heart of the chick shows itself in

the thirty-eighth hour, and that the first trace of red blood

showed in the forty-first hour. By his investigations upon the

lower animals he attempted to confirm the theory that since the

creation of genus every individual is derived from a preceding

individual--the existing theory of preformation, in which he

believed, and which taught that "every individual is fully and

completely preformed in the germ, simply growing from microscopic

to visible proportions, without developing any new parts."

In physiology, besides his studies of the nervous system, Haller

studied the mechanism of respiration, refuting the teachings of

Hamberger (1697-1755), who maintained that the lungs contract

independently. Haller, however, in common with his

contemporaries, failed utterly to understand the true function of

the lungs. The great physiologist's influence upon practical

medicine, while most profound, was largely indirect. He was a

theoretical rather than a practical physician, yet he is credited

with being the first physician to use the watch in counting the



A great contemporary of Haller was Giovanni Battista Morgagni

(1682-1771), who pursued what Sydenham had neglected, the

investigation in anatomy, thus supplying a necessary counterpart

to the great Englishman's work. Morgagni's investigations were

directed chiefly to the study of morbid anatomy--the study of the

structure of diseased tissue, both during life and post mortem,

in contrast to the normal anatomical structures. This work cannot

be said to have originated with him; for as early as 1679 Bonnet

had made similar, although less extensive, studies; and later

many investigators, such as Lancisi and Haller, had made

post-mortem studies. But Morgagni's De sedibus et causis

morborum per anatomen indagatis was the largest, most accurate,

and best-illustrated collection of cases that had ever been

brought together, and marks an epoch in medical science. From the

time of the publication of Morgagni's researches, morbid anatomy

became a recognized branch of the medical science, and the effect

of the impetus thus given it has been steadily increasing since

that time.


William Hunter (1718-1783) must always be remembered as one of

the greatest physicians and anatomists of the eighteenth century,

and particularly as the first great teacher of anatomy in

England; but his fame has been somewhat overshadowed by that of

his younger brother John.

Hunter had been intended and educated for the Church, but on the

advice of the surgeon William Cullen he turned his attention to

the study of medicine. His first attempt at teaching was in 1746,

when he delivered a series of lectures on surgery for the Society

of Naval Practitioners. These lectures proved so interesting and

instructive that he was at once invited to give others, and his

reputation as a lecturer was soon established. He was a natural

orator and story-teller, and he combined with these attractive

qualities that of thoroughness and clearness in demonstrations,

and although his lectures were two hours long he made them so

full of interest that his pupils seldom tired of listening. He

believed that he could do greater good to the world by "publicly

teaching his art than by practising it," and even during the last

few days of his life, when he was so weak that his friends

remonstrated against it, he continued his teaching, fainting from

exhaustion at the end of his last lecture, which preceded his

death by only a few days.

For many years it was Hunter's ambition to establish a museum

where the study of anatomy, surgery, and medicine might be

advanced, and in 1765 he asked for a grant of a plot of ground

for this purpose, offering to spend seven thousand pounds on its,

erection besides endowing it with a professorship of anatomy. Not

being able to obtain this grant, however, he built a house, in

which were lecture and dissecting rooms, and his museum. In this

museum were anatomical preparations, coins, minerals, and

natural-history specimens.

Hunter's weakness was his love of controversy and his resentment

of contradiction. This brought him into strained relations with

many of the leading physicians of his time, notably his own

brother John, who himself was probably not entirely free from

blame in the matter. Hunter is said to have excused his own

irritability on the grounds that being an anatomist, and

accustomed to "the passive submission of dead bodies,"

contradictions became the more unbearable. Many of the

physiological researches begun by him were carried on and

perfected by his more famous brother, particularly his

investigations of the capillaries, but he added much to the

anatomical knowledge of several structures of the body, notably

as to the structure of cartilages and joints.


In Abbot Islip's chapel in Westminster Abbey, close to the

resting-place of Ben Jonson, rest the remains of John Hunter

(1728-1793), famous in the annals of medicine as among the

greatest physiologists and surgeons that the world has ever

produced: a man whose discoveries and inventions are counted by

scores, and whose field of research was only limited by the

outermost boundaries of eighteenth-century science, although his

efforts were directed chiefly along the lines of his profession.

Until about twenty years of age young Hunter had shown little

aptitude for study, being unusually fond of out-door sports and

amusements; but about that time, realizing that some occupation

must be selected, he asked permission of his brother William to

attempt some dissections in his anatomical school in London. To

the surprise of his brother he made this dissection unusually

well; and being given a second, he acquitted himself with such

skill that his brother at once predicted that he would become a

great anatomist. Up to this time he had had no training of any

kind to prepare him for his professional career, and knew little

of Greek or Latin--languages entirely unnecessary for him, as he

proved in all of his life work. Ottley tells the story that,

when twitted with this lack of knowledge of the "dead languages"

in after life, he said of his opponent, "I could teach him that

on the dead body which he never knew in any language, dead or


By his second year in dissection he had become so skilful that he

was given charge of some of the classes in his brother's school;

in 1754 he became a surgeon's pupil in St. George's Hospital, and

two years later house-surgeon. Having by overwork brought on

symptoms that seemed to threaten consumption, he accepted the

position of staff-surgeon to an expedition to Belleisle in 1760,

and two years later was serving with the English army at

Portugal. During all this time he was constantly engaged in

scientific researches, many of which, such as his observations of

gun-shot wounds, he put to excellent use in later life. On

returning to England much improved in health in 1763, he entered

at once upon his career as a London surgeon, and from that time

forward his progress was a practically uninterrupted series of

successes in his profession.

Hunter's work on the study of the lymphatics was of great service

to the medical profession. This important net-work of minute

vessels distributed throughout the body had recently been made

the object of much study, and various students, including Haller,

had made extensive investigations since their discovery by

Asellius. But Hunter, in 1758, was the first to discover the

lymphatics in the neck of birds, although it was his brother

William who advanced the theory that the function of these

vessels was that of absorbents. One of John Hunter's pupils,

William Hewson (1739-1774), first gave an account, in 1768, of

the lymphatics in reptiles and fishes, and added to his teacher's

investigations of the lymphatics in birds. These studies of the

lymphatics have been regarded, perhaps with justice, as Hunter's

most valuable contributions to practical medicine.

In 1767 he met with an accident by which he suffered a rupture of

the tendo Achillis--the large tendon that forms the attachment of

the muscles of the calf to the heel. From observations of this

accident, and subsequent experiments upon dogs, he laid the

foundation for the now simple and effective operation for the

cure of club feet and other deformities involving the tendons.

In 1772 he moved into his residence at Earlscourt, Brompton,

where he gathered about him a great menagerie of animals, birds,

reptiles, insects, and fishes, which he used in his physiological

and surgical experiments. Here he performed a countless number of

experiments--more, probably, than "any man engaged in

professional practice has ever conducted." These experiments

varied in nature from observations of the habits of bees and

wasps to major surgical operations performed upon hedgehogs,

dogs, leopards, etc. It is said that for fifteen years he kept a

flock of geese for the sole purpose of studying the process of

development in eggs.

Hunter began his first course of lectures in 1772, being forced

to do this because he had been so repeatedly misquoted, and

because he felt that he could better gauge his own knowledge in

this way. Lecturing was a sore trial to him, as he was extremely

diffident, and without writing out his lectures in advance he was

scarcely able to speak at all. In this he presented a marked

contrast to his brother William, who was a fluent and brilliant

speaker. Hunter's lectures were at best simple readings of the

facts as he had written them, the diffident teacher seldom

raising his eyes from his manuscript and rarely stopping until

his complete lecture had been read through. His lectures were,

therefore, instructive rather than interesting, as he used

infinite care in preparing them; but appearing before his classes

was so dreaded by him that he is said to have been in the habit

of taking a half-drachm of laudanum before each lecture to nerve

him for the ordeal. One is led to wonder by what name he shall

designate that quality of mind that renders a bold and fearless

surgeon like Hunter, who is undaunted in the face of hazardous

and dangerous operations, a stumbling, halting, and "frightened"

speaker before a little band of, at most, thirty young medical

students. And yet this same thing is not unfrequently seen among

the boldest surgeons.

Hunter's Operation for the Cure of Aneurisms

It should be an object-lesson to those who, ignorantly or

otherwise, preach against the painless vivisection as practised

to-day, that by the sacrifice of a single deer in the cause of

science Hunter discovered a fact in physiology that has been the

means of saving thousands of human lives and thousands of human

bodies from needless mutilation. We refer to the discovery of the

"collateral circulation" of the blood, which led, among other

things, to Hunter's successful operation upon aneurisms.

Simply stated, every organ or muscle of the body is supplied by

one large artery, whose main trunk distributes the blood into its

lesser branches, and thence through the capillaries. Cutting off

this main artery, it would seem, should cut off entirely the

blood-supply to the particular organ which is supplied by this

vessel; and until the time of Hunter's demonstration this belief

was held by most physiologists. But nature has made a provision

for this possible stoppage of blood-supply from a single source,

and has so arranged that some of the small arterial branches

coming from the main supply-trunk are connected with other

arterial branches coming from some other supply-trunk. Under

normal conditions the main arterial trunks supply their

respective organs, the little connecting arterioles playing an

insignificant part. But let the main supply-trunk be cut off or

stopped for whatever reason, and a remarkable thing takes place.

The little connecting branches begin at once to enlarge and draw

blood from the neighboring uninjured supply-trunk, This

enlargement continues until at last a new route for the

circulation has been established, the organ no longer depending

on the now defunct original arterial trunk, but getting on as

well as before by this "collateral" circulation that has been


The thorough understanding of this collateral circulation is one

of the most important steps in surgery, for until it was

discovered amputations were thought necessary in such cases as

those involving the artery supplying a leg or arm, since it was

supposed that, the artery being stopped, death of the limb and

the subsequent necessity for amputation were sure to follow.

Hunter solved this problem by a single operation upon a deer, and

his practicality as a surgeon led him soon after to apply this

knowledge to a certain class of surgical cases in a most

revolutionary and satisfactory manner.

What led to Hunter's far-reaching discovery was his investigation

as to the cause of the growth of the antlers of the deer. Wishing

to ascertain just what part the blood-supply on the opposite

sides of the neck played in the process of development, or,

perhaps more correctly, to see what effect cutting off the main

blood-supply would have, Hunter had one of the deer of Richmond

Park caught and tied, while he placed a ligature around one of

the carotid arteries--one of the two principal arteries that

supply the head with blood. He observed that shortly after this

the antler (which was only half grown and consequently very

vascular) on the side of the obliterated artery became cold to

the touch--from the lack of warmth-giving blood. There was

nothing unexpected in this, and Hunter thought nothing of it

until a few days later, when he found, to his surprise, that the

antler had become as warm as its fellow, and was apparently

increasing in size. Puzzled as to how this could be, and

suspecting that in some way his ligature around the artery had

not been effective, he ordered the deer killed, and on

examination was astonished to find that while his ligature had

completely shut off the blood-supply from the source of that

carotid artery, the smaller arteries had become enlarged so as to

supply the antler with blood as well as ever, only by a different


Hunter soon had a chance to make a practical application of the

knowledge thus acquired. This was a case of popliteal aneurism,

operations for which had heretofore proved pretty uniformly

fatal. An aneurism, as is generally understood, is an enlargement

of a certain part of an artery, this enlargement sometimes

becoming of enormous size, full of palpitating blood, and likely

to rupture with fatal results at any time. If by any means the

blood can be allowed to remain quiet for even a few hours in this

aneurism it will form a clot, contract, and finally be absorbed

and disappear without any evil results. The problem of keeping

the blood quiet, with the heart continually driving it through

the vessel, is not a simple one, and in Hunter's time was

considered so insurmountable that some surgeons advocated

amputation of any member having an aneurism, while others cut

down upon the tumor itself and attempted to tie off the artery

above and below. The first of these operations maimed the patient

for life, while the second was likely to prove fatal.

In pondering over what he had learned about collateral

circulation and the time required for it to become fully

established, Hunter conceived the idea that if the blood-supply

was cut off from above the aneurism, thus temporarily preventing

the ceaseless pulsations from the heart, this blood would

coagulate and form a clot before the collateral circulation could

become established or could affect it. The patient upon whom he

performed his now celebrated operation was afflicted with a

popliteal aneurism--that is, the aneurism was located on the

large popliteal artery just behind the knee-joint. Hunter,

therefore, tied off the femoral, or main supplying artery in the

thigh, a little distance above the aneurism. The operation was

entirely successful, and in six weeks' time the patient was able

to leave the hospital, and with two sound limbs. Naturally the

simplicity and success of this operation aroused the attention of

Europe, and, alone, would have made the name of Hunter immortal

in the annals of surgery. The operation has ever since been

called the "Hunterian" operation for aneurism, but there is

reason to believe that Dominique Anel (born about 1679) performed

a somewhat similar operation several years earlier. It is

probable, however, that Hunter had never heard of this work of

Anel, and that his operation was the outcome of his own

independent reasoning from the facts he had learned about

collateral circulation. Furthermore, Hunter's mode of operation

was a much better one than Anel's, and, while Anel's must claim

priority, the credit of making it widely known will always be


The great services of Hunter were recognized both at home and

abroad, and honors and positions of honor and responsibility were

given him. In 1776 he was appointed surgeon-extraordinary to the

king; in 1783 he was elected a member of the Royal Society of

Medicine and of the Royal Academy of Surgery at Paris; in 1786 he

became deputy surgeon-general of the army; and in 1790 he was

appointed surgeon-general and inspector-general of hospitals. All

these positions he filled with credit, and he was actively

engaged in his tireless pursuit of knowledge and in discharging

his many duties when in October, 1793, he was stricken while

addressing some colleagues, and fell dead in the arms of a



Hunter's great rival among contemporary physiologists was the

Italian Lazzaro Spallanzani (1729-1799), one of the most

picturesque figures in the history of science. He was not

educated either as a scientist or physician, devoting, himself at

first to philosophy and the languages, afterwards studying law,

and later taking orders. But he was a keen observer of nature and

of a questioning and investigating mind, so that he is remembered

now chiefly for his discoveries and investigations in the

biological sciences. One important demonstration was his

controversion of the theory of abiogenesis, or "spontaneous

generation," as propounded by Needham and Buffon. At the time of

Needham's experiments it had long been observed that when animal

or vegetable matter had lain in water for a little time--long

enough for it to begin to undergo decomposition--the water became

filled with microscopic creatures, the "infusoria animalculis."

This would tend to show, either that the water or the animal or

vegetable substance contained the "germs" of these minute

organisms, or else that they were generated spontaneously. It was

known that boiling killed these animalcules, and Needham agreed,

therefore, that if he first heated the meat or vegetables, and

also the water containing them, and then placed them in

hermetically scaled jars--if he did this, and still the

animalcules made their appearance, it would be proof-positive

that they had been generated spontaneously. Accordingly be made

numerous experiments, always with the same results--that after a

few days the water was found to swarm with the microscopic

creatures. The thing seemed proven beyond question--providing, of

course, that there had been no slips in the experiments.

But Abbe Spallanzani thought that he detected such slips in

Needham's experiment. The possibility of such slips might come

in several ways: the contents of the jar might not have been

boiled for a sufficient length of time to kill all the germs, or

the air might not have been excluded completely by the sealing

process. To cover both these contingencies, Spallanzani first

hermetically sealed the glass vessels and then boiled them for

three-quarters of an hour. Under these circumstances no

animalcules ever made their appearance--a conclusive

demonstration that rendered Needham's grounds for his theory at

once untenable.[2]

Allied to these studies of spontaneous generation were

Spallanzani's experiments and observations on the physiological

processes of generation among higher animals. He experimented

with frogs, tortoises, and dogs; and settled beyond question the

function of the ovum and spermatozoon. Unfortunately he

misinterpreted the part played by the spermatozoa in believing

that their surrounding fluid was equally active in the

fertilizing process, and it was not until some forty years later

(1824) that Dumas corrected this error.


Among the most interesting researches of Spallanzani were his

experiments to prove that digestion, as carried on in the

stomach, is a chemical process. In this he demonstrated, as Rene

Reaumur had attempted to demonstrate, that digestion could be

carried on outside the walls of the stomach as an ordinary

chemical reaction, using the gastric juice as the reagent for

performing the experiment. The question as to whether the stomach

acted as a grinding or triturating organ, rather than as a

receptacle for chemical action, had been settled by Reaumur and

was no longer a question of general dispute. Reaumur had

demonstrated conclusively that digestion would take place in the

stomach in the same manner and the same time if the substance to

be digested was protected from the peristalic movements of the

stomach and subjected to the action of the gastric juice only. He

did this by introducing the substances to be digested into the

stomach in tubes, and thus protected so that while the juices of

the stomach could act upon them freely they would not be affected

by any movements of the organ.

Following up these experiments, he attempted to show that

digestion could take place outside the body as well as in it, as

it certainly should if it were a purely chemical process. He

collected quantities of gastric juice, and placing it in suitable

vessels containing crushed grain or flesh, kept the mixture at

about the temperature of the body for several hours. After

repeated experiments of this kind, apparently conducted with

great care, Reaumur reached the conclusion that "the gastric

juice has no more effect out of the living body in dissolving or

digesting the food than water, mucilage, milk, or any other bland

fluid."[3] Just why all of these experiments failed to

demonstrate a fact so simple does not appear; but to Spallanzani,

at least, they were by no means conclusive, and he proceeded to

elaborate upon the experiments of Reaumur. He made his

experiments in scaled tubes exposed to a certain degree of heat,

and showed conclusively that the chemical process does go on,

even when the food and gastric juice are removed from their

natural environment in the stomach. In this he was opposed by

many physiologists, among them John Hunter, but the truth of his

demonstrations could not be shaken, and in later years we find

Hunter himself completing Spallanzani's experiments by his

studies of the post-mortem action of the gastric juice upon the

stomach walls.

That Spallanzani's and Hunter's theories of the action of the

gastric juice were not at once universally accepted is shown by

an essay written by a learned physician in 1834. In speaking of

some of Spallanzani's demonstrations, he writes: "In some of the

experiments, in order to give the flesh or grains steeped in the

gastric juice the same temperature with the body, the phials were

introduced under the armpits. But this is not a fair mode of

ascertaining the effects of the gastric juice out of the body;

for the influence which life may be supposed to have on the

solution of the food would be secured in this case. The

affinities connected with life would extend to substances in

contact with any part of the system: substances placed under the

armpits are not placed at least in the same circumstances with

those unconnected with a living animal." But just how this writer

reaches the conclusion that "the experiments of Reaumur and

Spallanzani give no evidence that the gastric juice has any

peculiar influence more than water or any other bland fluid in

digesting the food"[4] is difficult to understand.

The concluding touches were given to the new theory of digestion

by John Hunter, who, as we have seen, at first opposed

Spallanzani, but who finally became an ardent champion of the

chemical theory. Hunter now carried Spallanzani's experiments

further and proved the action of the digestive fluids after

death. For many years anatomists had been puzzled by pathological

lesion of the stomach, found post mortem, when no symptoms of any

disorder of the stomach had been evinced during life. Hunter

rightly conceived that these lesions were caused by the action of

the gastric juice, which, while unable to act upon the living

tissue, continued its action chemically after death, thus

digesting the walls of the stomach in which it had been formed.

And, as usual with his observations, be turned this discovery to

practical use in accounting for certain phenomena of digestion.

The following account of the stomach being digested after death

was written by Hunter at the desire of Sir John Pringle, when he

was president of the Royal Society, and the circumstance which

led to this is as follows: "I was opening, in his presence, the

body of a patient of his own, where the stomach was in part

dissolved, which appeared to him very unaccountable, as there had

been no previous symptom that could have led him to suspect any

disease in the stomach. I took that opportunity of giving him my

ideas respecting it, and told him that I had long been making

experiments on digestion, and considered this as one of the facts

which proved a converting power in the gastric juice. . . . There

are a great many powers in nature which the living principle does

not enable the animal matter, with which it is combined, to

resist--viz., the mechanical and most of the strongest chemical

solvents. It renders it, however, capable of resisting the powers

of fermentation, digestion, and perhaps several others, which are

well known to act on the same matter when deprived of the living

principle and entirely to decompose it. "

Hunter concludes his paper with the following paragraph: "These

appearances throw considerable light on the principle of

digestion, and show that it is neither a mechanical power, nor

contractions of the stomach, nor heat, but something secreted in

the coats of the stomach, and thrown into its cavity, which there

animalizes the food or assimilates it to the nature of the blood.

The power of this juice is confined or limited to certain

substances, especially of the vegetable and animal kingdoms; and

although this menstruum is capable of acting independently of the

stomach, yet it is indebted to that viscus for its



It is a curious commentary on the crude notions of mechanics of

previous generations that it should have been necessary to prove

by experiment that the thin, almost membranous stomach of a

mammal has not the power to pulverize, by mere attrition, the

foods that are taken into it. However, the proof was now for the

first time forthcoming, and the question of the general character

of the function of digestion was forever set at rest. Almost

simultaneously with this great advance, corresponding progress

was made in an allied field: the mysteries of respiration were

at last cleared up, thanks to the new knowledge of chemistry. The

solution of the problem followed almost as a matter of course

upon the advances of that science in the latter part of the

century. Hitherto no one since Mayow, of the previous century,

whose flash of insight had been strangely overlooked and

forgotten, had even vaguely surmised the true function of the

lungs. The great Boerhaave had supposed that respiration is

chiefly important as an aid to the circulation of the blood; his

great pupil, Haller, had believed to the day of his death in 1777

that the main purpose of the function is to form the voice. No

genius could hope to fathom the mystery of the lungs so long as

air was supposed to be a simple element, serving a mere

mechanical purpose in the economy of the earth.

But the discovery of oxygen gave the clew, and very soon all the

chemists were testing the air that came from the lungs--Dr.

Priestley, as usual, being in the van. His initial experiments

were made in 1777, and from the outset the problem was as good as

solved. Other experimenters confirmed his results in all their

essentials--notably Scheele and Lavoisier and Spallanzani and

Davy. It was clearly established that there is chemical action

in the contact of the air with the tissue of the lungs; that some

of the oxygen of the air disappears, and that carbonic-acid gas

is added to the inspired air. It was shown, too, that the blood,

having come in contact with the air, is changed from black to red

in color. These essentials were not in dispute from the first.

But as to just what chemical changes caused these results was the

subject of controversy. Whether, for example, oxygen is actually

absorbed into the blood, or whether it merely unites with carbon

given off from the blood, was long in dispute.

Each of the main disputants was biased by his own particular

views as to the moot points of chemistry. Lavoisier, for

example, believed oxygen gas to be composed of a metal oxygen

combined with the alleged element heat; Dr. Priestley thought it

a compound of positive electricity and phlogiston; and Humphry

Davy, when he entered the lists a little later, supposed it to be

a compound of oxygen and light. Such mistaken notions naturally

complicated matters and delayed a complete understanding of the

chemical processes of respiration. It was some time, too, before

the idea gained acceptance that the most important chemical

changes do not occur in the lungs themselves, but in the ultimate

tissues. Indeed, the matter was not clearly settled at the close

of the century. Nevertheless, the problem of respiration had

been solved in its essentials. Moreover, the vastly important

fact had been established that a process essentially identical

with respiration is necessary to the existence not only of all

creatures supplied with lungs, but to fishes, insects, and even

vegetables--in short, to every kind of living organism.


Some interesting experiments regarding vegetable respiration were

made just at the close of the century by Erasmus Darwin, and

recorded in his Botanic Garden as a foot-note to the verse:

"While spread in air the leaves respiring play."

These notes are worth quoting at some length, as they give a

clear idea of the physiological doctrines of the time (1799),

while taking advance ground as to the specific matter in


"There have been various opinions," Darwin says, "concerning the

use of the leaves of plants in the vegetable economy. Some have

contended that they are perspiratory organs. This does not seem

probable from an experiment of Dr. Hales, Vegetable Statics, p.

30. He, found, by cutting off branches of trees with apples on

them and taking off the leaves, that an apple exhaled about as

much as two leaves the surfaces of which were nearly equal to the

apple; whence it would appear that apples have as good a claim to

be termed perspiratory organs as leaves. Others have believed

them excretory organs of excrementitious juices, but as the vapor

exhaled from vegetables has no taste, this idea is no more

probable than the other; add to this that in most weathers they

do not appear to perspire or exhale at all.

"The internal surface of the lungs or air-vessels in men is said

to be equal to the external surface of the whole body, or almost

fifteen square feet; on this surface the blood is exposed to the

influence of the respired air through the medium, however, of a

thin pellicle; by this exposure to the air it has its color

changed from deep red to bright scarlet, and acquires something

so necessary to the existence of life that we can live scarcely a

minute without this wonderful process.

"The analogy between the leaves of plants and the lungs or gills

of animals seems to embrace so many circumstances that we can

scarcely withhold our consent to their performing similar


"1. The great surface of leaves compared to that of the trunk

and branches of trees is such that it would seem to be an organ

well adapted for the purpose of exposing the vegetable juices to

the influence of the air; this, however, we shall see afterwards

is probably performed only by their upper surfaces, yet even in

this case the surface of the leaves in general bear a greater

proportion to the surface of the tree than the lungs of animals

to their external surfaces.

"2. In the lung of animals the blood, after having been exposed

to the air in the extremities of the pulmonary artery, is changed

in color from deep red to bright scarlet, and certainly in some

of its essential properties it is then collected by the pulmonary

vein and returned to the heart. To show a similarity of

circumstances in the leaves of plants, the following experiment

was made, June 24, 1781. A stalk with leaves and seed-vessels of

large spurge (Euphorbia helioscopia) had been several days placed

in a decoction of madder (Rubia tinctorum) so that the lower part

of the stem and two of the undermost leaves were immersed in it.

After having washed the immersed leaves in clear water I could

readily discover the color of the madder passing along the middle

rib of each leaf. The red artery was beautifully visible on the

under and on the upper surface of the leaf; but on the upper side

many red branches were seen going from it to the extremities of

the leaf, which on the other side were not visible except by

looking through it against the light. On this under side a system

of branching vessels carrying a pale milky fluid were seen coming

from the extremities of the leaf, and covering the whole under

side of it, and joining two large veins, one on each side of the

red artery in the middle rib of the leaf, and along with it

descending to the foot-stalk or petiole. On slitting one of these

leaves with scissors, and having a magnifying-glass ready, the

milky blood was seen oozing out of the returning veins on each

side of the red artery in the middle rib, but none of the red

fluid from the artery.

"All these appearances were more easily seen in a leaf of Picris

treated in the same manner; for in this milky plant the stems and

middle rib of the leaves are sometimes naturally colored reddish,

and hence the color of the madder seemed to pass farther into the

ramifications of their leaf-arteries, and was there beautifully

visible with the returning branches of milky veins on each side."

Darwin now goes on to draw an incorrect inference from his


"3. From these experiments," he says, "the upper surface of the

leaf appeared to be the immediate organ of respiration, because

the colored fluid was carried to the extremities of the leaf by

vessels most conspicuous on the upper surface, and there changed

into a milky fluid, which is the blood of the plant, and then

returned by concomitant veins on the under surface, which were

seen to ooze when divided with scissors, and which, in Picris,

particularly, render the under surface of the leaves greatly

whiter than the upper one."

But in point of fact, as studies of a later generation were to

show, it is the under surface of the leaf that is most abundantly

provided with stomata, or "breathing-pores." From the stand-point

of this later knowledge, it is of interest to follow our author a

little farther, to illustrate yet more fully the possibility of

combining correct observations with a faulty inference.

"4. As the upper surface of leaves constitutes the organ of

respiration, on which the sap is exposed in the termination of

arteries beneath a thin pellicle to the action of the atmosphere,

these surfaces in many plants strongly repel moisture, as cabbage

leaves, whence the particles of rain lying over their surfaces

without touching them, as observed by Mr. Melville (Essays

Literary and Philosophical: Edinburgh), have the appearance of

globules of quicksilver. And hence leaves with the upper

surfaces on water wither as soon as in the dry air, but continue

green for many days if placed with the under surface on water, as

appears in the experiments of Monsieur Bonnet (Usage des

Feuilles). Hence some aquatic plants, as the water-lily

(Nymphoea), have the lower sides floating on the water, while the

upper surfaces remain dry in the air.

"5. As those insects which have many spiracula, or breathing

apertures, as wasps and flies, are immediately suffocated by

pouring oil upon them, I carefully covered with oil the surfaces

of several leaves of phlomis, of Portugal laurel, and balsams,

and though it would not regularly adhere, I found them all die in

a day or two.

"It must be added that many leaves are furnished with muscles

about their foot-stalks, to turn their surfaces to the air or

light, as mimosa or Hedysarum gyrans. From all these analogies I

think there can be no doubt but that leaves of trees are their

lungs, giving out a phlogistic material to the atmosphere, and

absorbing oxygen, or vital air.

"6. The great use of light to vegetation would appear from this

theory to be by disengaging vital air from the water which they

perspire, and thence to facilitate its union with their blood

exposed beneath the thin surface of their leaves; since when pure

air is thus applied it is probable that it can be more readily

absorbed. Hence, in the curious experiments of Dr. Priestley and

Mr. Ingenhouz, some plants purified less air than others--that

is, they perspired less in the sunshine; and Mr. Scheele found

that by putting peas into water which about half covered them

they converted the vital air into fixed air, or carbonic-acid

gas, in the same manner as in animal respiration.

"7. The circulation in the lungs or leaves of plants is very

similar to that of fish. In fish the blood, after having passed

through their gills, does not return to the heart as from the

lungs of air-breathing animals, but the pulmonary vein taking the

structure of an artery after having received the blood from the

gills, which there gains a more florid color, distributes it to

the other parts of their bodies. The same structure occurs in the

livers of fish, whence we see in those animals two circulations

independent of the power of the heart--viz., that beginning at

the termination of the veins of the gills and branching through

the muscles, and that which passes through the liver; both which

are carried on by the action of those respective arteries and


Darwin is here a trifle fanciful in forcing the analogy between

plants and animals. The circulatory system of plants is really

not quite so elaborately comparable to that of fishes as he

supposed. But the all-important idea of the uniformity underlying

the seeming diversity of Nature is here exemplified, as elsewhere

in the writings of Erasmus Darwin; and, more specifically, a

clear grasp of the essentials of the function of respiration is

fully demonstrated.


Several causes conspired to make exploration all the fashion

during the closing epoch of the eighteenth century. New aid to

the navigator had been furnished by the perfected compass and

quadrant, and by the invention of the chronometer; medical

science had banished scurvy, which hitherto had been a perpetual

menace to the voyager; and, above all, the restless spirit of the

age impelled the venturesome to seek novelty in fields altogether

new. Some started for the pole, others tried for a northeast or

northwest passage to India, yet others sought the great

fictitious antarctic continent told of by tradition. All these of

course failed of their immediate purpose, but they added much to

the world's store of knowledge and its fund of travellers' tales.

Among all these tales none was more remarkable than those which

told of strange living creatures found in antipodal lands. And

here, as did not happen in every field, the narratives were often

substantiated by the exhibition of specimens that admitted no

question. Many a company of explorers returned more or less laden

with such trophies from the animal and vegetable kingdoms, to the

mingled astonishment, delight, and bewilderment of the closet

naturalists. The followers of Linnaeus in the "golden age of

natural history," a few decades before, had increased the number

of known species of fishes to about four hundred, of birds to one

thousand, of insects to three thousand, and of plants to ten

thousand. But now these sudden accessions from new territories

doubled the figure for plants, tripled it for fish and birds, and

brought the number of described insects above twenty thousand.

Naturally enough, this wealth of new material was sorely puzzling

to the classifiers. The more discerning began to see that the

artificial system of Linnaeus, wonderful and useful as it had

been, must be advanced upon before the new material could be

satisfactorily disposed of. The way to a more natural system,

based on less arbitrary signs, had been pointed out by Jussieu in

botany, but the zoologists were not prepared to make headway

towards such a system until they should gain a wider

understanding of the organisms with which they had to deal

through comprehensive studies of anatomy. Such studies of

individual forms in their relations to the entire scale of

organic beings were pursued in these last decades of the century,

but though two or three most important generalizations were

achieved (notably Kaspar Wolff's conception of the cell as the

basis of organic life, and Goethe's all-important doctrine of

metamorphosis of parts), yet, as a whole, the work of the

anatomists of the period was germinative rather than

fruit-bearing. Bichat's volumes, telling of the recognition of

the fundamental tissues of the body, did not begin to appear till

the last year of the century. The announcement by Cuvier of the

doctrine of correlation of parts bears the same date, but in

general the studies of this great naturalist, which in due time

were to stamp him as the successor of Linnaeus, were as yet only

fairly begun.



We have seen that the focal points of the physiological world

towards the close of the eighteenth century were Italy and

England, but when Spallanzani and Hunter passed away the scene

shifted to France. The time was peculiarly propitious, as the

recent advances in many lines of science had brought fresh data

for the student of animal life which were in need of

classification, and, as several minds capable of such a task were

in the field, it was natural that great generalizations should

have come to be quite the fashion. Thus it was that Cuvier came

forward with a brand-new classification of the animal kingdom,

establishing four great types of being, which he called

vertebrates, mollusks, articulates, and radiates. Lamarck had

shortly before established the broad distinction between animals

with and those without a backbone; Cuvier's Classification

divided the latter--the invertebrates--into three minor groups.

And this division, familiar ever since to all students of

zoology, has only in very recent years been supplanted, and then

not by revolution, but by a further division, which the elaborate

recent studies of lower forms of life seemed to make desirable.

In the course of those studies of comparative anatomy which led

to his new classification, Cuvier's attention was called

constantly to the peculiar co-ordination of parts in each

individual organism. Thus an animal with sharp talons for

catching living prey--as a member of the cat tribe--has also

sharp teeth, adapted for tearing up the flesh of its victim, and

a particular type of stomach, quite different from that of

herbivorous creatures. This adaptation of all the parts of the

animal to one another extends to the most diverse parts of the

organism, and enables the skilled anatomist, from the observation

of a single typical part, to draw inferences as to the structure

of the entire animal--a fact which was of vast aid to Cuvier in

his studies of paleontology. It did not enable Cuvier, nor does

it enable any one else, to reconstruct fully the extinct animal

from observation of a single bone, as has sometimes been

asserted, but what it really does establish, in the hands of an

expert, is sufficiently astonishing.

"While the study of the fossil remains of the greater quadrupeds

is more satisfactory," he writes, "by the clear results which it

affords, than that of the remains of other animals found in a

fossil state, it is also complicated with greater and more

numerous difficulties. Fossil shells are usually found quite

entire, and retaining all the characters requisite for comparing

them with the specimens contained in collections of natural

history, or represented in the works of naturalists. Even the

skeletons of fishes are found more or less entire, so that the

general forms of their bodies can, for the most part, be

ascertained, and usually, at least, their generic and specific

characters are determinable, as these are mostly drawn from their

solid parts. In quadrupeds, on the contrary, even when their

entire skeletons are found, there is great difficulty in

discovering their distinguishing characters, as these are chiefly

founded upon their hairs and colors and other marks which have

disappeared previous to their incrustation. It is also very rare

to find any fossil skeletons of quadrupeds in any degree

approaching to a complete state, as the strata for the most part

only contain separate bones, scattered confusedly and almost

always broken and reduced to fragments, which are the only means

left to naturalists for ascertaining the species or genera to

which they have belonged.

"Fortunately comparative anatomy, when thoroughly understood,

enables us to surmount all these difficulties, as a careful

application of its principles instructs us in the correspondences

and dissimilarities of the forms of organized bodies of different

kinds, by which each may be rigorously ascertained from almost

every fragment of its various parts and organs.

"Every organized individual forms an entire system of its own,

all the parts of which naturally correspond, and concur to

produce a certain definite purpose, by reciprocal reaction, or by

combining towards the same end. Hence none of these separate

parts can change their forms without a corresponding change in

the other parts of the same animal, and consequently each of

these parts, taken separately, indicates all the other parts to

which it has belonged. Thus, as I have elsewhere shown, if the

viscera of an animal are so organized as only to be fitted for

the digestion of recent flesh, it is also requisite that the jaws

should be so constructed as to fit them for devouring prey; the

claws must be constructed for seizing and tearing it to pieces;

the teeth for cutting and dividing its flesh; the entire system

of the limbs, or organs of motion, for pursuing and overtaking

it; and the organs of sense for discovering it at a distance.

Nature must also have endowed the brain of the animal with

instincts sufficient for concealing itself and for laying plans

to catch its necessary victims. . . . . . . . . .

"To enable the animal to carry off its prey when seized, a

corresponding force is requisite in the muscles which elevate the

head, and this necessarily gives rise to a determinate form of

the vertebrae to which these muscles are attached and of the

occiput into which they are inserted. In order that the teeth of

a carnivorous animal may be able to cut the flesh, they require

to be sharp, more or less so in proportion to the greater or less

quantity of flesh that they have to cut. It is requisite that

their roots should be solid and strong, in proportion to the

quantity and size of the bones which they have to break to

pieces. The whole of these circumstances must necessarily

influence the development and form of all the parts which

contribute to move the jaws. . . . . . . . . .

After these observations, it will be easily seen that similar

conclusions may be drawn with respect to the limbs of carnivorous

animals, which require particular conformations to fit them for

rapidity of motion in general; and that similar considerations

must influence the forms and connections of the vertebrae and

other bones constituting the trunk of the body, to fit them for

flexibility and readiness of motion in all directions. The bones

also of the nose, of the orbit, and of the ears require certain

forms and structures to fit them for giving perfection to the

senses of smell, sight, and hearing, so necessary to animals of

prey. In short, the shape and structure of the teeth regulate the

forms of the condyle, of the shoulder-blade, and of the claws, in

the same manner as the equation of a curve regulates all its

other properties; and as in regard to any particular curve all

its properties may be ascertained by assuming each separate

property as the foundation of a particular equation, in the same

manner a claw, a shoulder-blade, a condyle, a leg or arm bone, or

any other bone separately considered, enables us to discover the

description of teeth to which they have belonged; and so also

reciprocally we may determine the forms of the other bones from

the teeth. Thus commencing our investigations by a careful

survey of any one bone by itself, a person who is sufficiently

master of the laws of organic structure may, as it were,

reconstruct the whole animal to which that bone belonged."[1]

We have already pointed out that no one is quite able to perform

the necromantic feat suggested in the last sentence; but the

exaggeration is pardonable in the enthusiast to whom the

principle meant so much and in whose hands it extended so far.

Of course this entire principle, in its broad outlines, is

something with which every student of anatomy had been familiar

from the time when anatomy was first studied, but the full

expression of the "law of co-ordination," as Cuvier called it,

had never been explicitly made before; and, notwithstanding its

seeming obviousness, the exposition which Cuvier made of it in

the introduction to his classical work on comparative anatomy,

which was published during the first decade of the nineteenth

century, ranks as a great discovery. It is one of those

generalizations which serve as guideposts to other discoveries.


Much the same thing may be said of another generalization

regarding the animal body, which the brilliant young French

physician Marie Francois Bichat made in calling attention to the

fact that each vertebrate organism, including man, has really two

quite different sets of organs--one set under volitional control,

and serving the end of locomotion, the other removed from

volitional control, and serving the ends of the "vital processes"

of digestion, assimilation, and the like. He called these sets of

organs the animal system and the organic system, respectively.

The division thus pointed out was not quite new, for Grimaud,

professor of physiology in the University of Montpellier, had

earlier made what was substantially the same classification of

the functions into "internal or digestive and external or

locomotive"; but it was Bichat's exposition that gave currency to

the idea.

Far more important, however, was another classification which

Bichat put forward in his work on anatomy, published just at the

beginning of the last century. This was the division of all

animal structures into what Bichat called tissues, and the

pointing out that there are really only a few kinds of these in

the body, making up all the diverse organs. Thus muscular organs

form one system; membranous organs another; glandular organs a

third; the vascular mechanism a fourth, and so on. The

distinction is so obvious that it seems rather difficult to

conceive that it could have been overlooked by the earliest

anatomists; but, in point of fact, it is only obvious because now

it has been familiarly taught for almost a century. It had never

been given explicit expression before the time of Bichat, though

it is said that Bichat himself was somewhat indebted for it to

his master, Desault, and to the famous alienist Pinel.

However that may be, it is certain that all subsequent anatomists

have found Bichat's classification of the tissues of the utmost

value in their studies of the animal functions. Subsequent

advances were to show that the distinction between the various

tissues is not really so fundamental as Bichat supposed, but that

takes nothing from the practical value of the famous


It was but a step from this scientific classification of tissues

to a similar classification of the diseases affecting them, and

this was one of the greatest steps towards placing medicine on

the plane of an exact science. This subject of these branches

completely fascinated Bichat, and he exclaimed, enthusiastically:

"Take away some fevers and nervous trouble, and all else belongs

to the kingdom of pathological anatomy." But out of this

enthusiasm came great results. Bichat practised as he preached,

and, believing that it was only possible to understand disease by

observing the symptoms carefully at the bedside, and, if the

disease terminated fatally, by post-mortem examination, he was so

arduous in his pursuit of knowledge that within a period of less

than six months he had made over six hundred autopsies--a record

that has seldom, if ever, been equalled. Nor were his efforts

fruitless, as a single example will suffice to show. By his

examinations he was able to prove that diseases of the chest,

which had formerly been classed under the indefinite name

"peripneumonia," might involve three different structures, the

pleural sac covering the lungs, the lung itself, and the

bronchial tubes, the diseases affecting these organs being known

respectively as pleuritis, pneumonia, and bronchitis, each one

differing from the others as to prognosis and treatment. The

advantage of such an exact classification needs no demonstration.


At the same time when these broad macroscopical distinctions were

being drawn there were other workers who were striving to go even

deeper into the intricacies of the animal mechanism with the aid

of the microscope. This undertaking, however, was beset with

very great optical difficulties, and for a long time little

advance was made upon the work of preceding generations. Two

great optical barriers, known technically as spherical and

chromatic aberration--the one due to a failure of the rays of

light to fall all in one plane when focalized through a lens, the

other due to the dispersive action of the lens in breaking the

white light into prismatic colors--confronted the makers of

microscopic lenses, and seemed all but insuperable. The making of

achromatic lenses for telescopes had been accomplished, it is

true, by Dolland in the previous century, by the union of lenses

of crown glass with those of flint glass, these two materials

having different indices of refraction and dispersion. But, aside

from the mechanical difficulties which arise when the lens is of

the minute dimensions required for use with the microscope, other

perplexities are introduced by the fact that the use of a wide

pencil of light is a desideratum, in order to gain sufficient

illumination when large magnification is to be secured.

In the attempt to overcome those difficulties, the foremost

physical philosophers of the time came to the aid of the best

opticians. Very early in the century, Dr. (afterwards Sir David)

Brewster, the renowned Scotch physicist, suggested that certain

advantages might accrue from the use of such gems as have high

refractive and low dispersive indices, in place of lenses made of

glass. Accordingly lenses were made of diamond, of sapphire, and

so on, and with some measure of success. But in 1812 a much more

important innovation was introduced by Dr. William Hyde

Wollaston, one of the greatest and most versatile, and, since the

death of Cavendish, by far the most eccentric of English natural

philosophers. This was the suggestion to use two plano-convex

lenses, placed at a prescribed distance apart, in lieu of the

single double-convex lens generally used. This combination

largely overcame the spherical aberration, and it gained

immediate fame as the "Wollaston doublet."

To obviate loss of light in such a doublet from increase of

reflecting surfaces, Dr. Brewster suggested filling the

interspace between the two lenses with a cement having the same

index of refraction as the lenses themselves--an improvement of

manifest advantage. An improvement yet more important was made by

Dr. Wollaston himself in the introduction of the diaphragm to

limit the field of vision between the lenses, instead of in front

of the anterior lens. A pair of lenses thus equipped Dr.

Wollaston called the periscopic microscope. Dr. Brewster

suggested that in such a lens the same object might be attained

with greater ease by grinding an equatorial groove about a thick

or globular lens and filling the groove with an opaque cement.

This arrangement found much favor, and came subsequently to be

known as a Coddington lens, though Mr. Coddington laid no claim

to being its inventor.

Sir John Herschel, another of the very great physicists of the

time, also gave attention to the problem of improving the

microscope, and in 1821 he introduced what was called an

aplanatic combination of lenses, in which, as the name implies,

the spherical aberration was largely done away with. It was

thought that the use of this Herschel aplanatic combination as an

eyepiece, combined with the Wollaston doublet for the objective,

came as near perfection as the compound microscope was likely

soon to come. But in reality the instrument thus constructed,

though doubtless superior to any predecessor, was so defective

that for practical purposes the simple microscope, such as the

doublet or the Coddington, was preferable to the more complicated


Many opticians, indeed, quite despaired of ever being able to

make a satisfactory refracting compound microscope, and some of

them had taken up anew Sir Isaac Newton's suggestion in reference

to a reflecting microscope. In particular, Professor Giovanni

Battista Amici, a very famous mathematician and practical

optician of Modena, succeeded in constructing a reflecting

microscope which was said to be superior to any compound

microscope of the time, though the events of the ensuing years

were destined to rob it of all but historical value. For there

were others, fortunately, who did not despair of the

possibilities of the refracting microscope, and their efforts

were destined before long to be crowned with a degree of success

not even dreamed of by any preceding generation.

The man to whom chief credit is due for directing those final

steps that made the compound microscope a practical implement

instead of a scientific toy was the English amateur optician

Joseph Jackson Lister. Combining mathematical knowledge with

mechanical ingenuity, and having the practical aid of the

celebrated optician Tulley, he devised formulae for the

combination of lenses of crown glass with others of flint glass,

so adjusted that the refractive errors of one were corrected or

compensated by the other, with the result of producing lenses of

hitherto unequalled powers of definition; lenses capable of

showing an image highly magnified, yet relatively free from those

distortions and fringes of color that had heretofore been so

disastrous to true interpretation of magnified structures.

Lister had begun his studies of the lens in 1824, but it was not

until 1830 that he contributed to the Royal Society the famous

paper detailing his theories and experiments. Soon after this

various continental opticians who had long been working along

similar lines took the matter up, and their expositions, in

particular that of Amici, introduced the improved compound

microscope to the attention of microscopists everywhere. And it

required but the most casual trial to convince the experienced

observers that a new implement of scientific research had been

placed in their hands which carried them a long step nearer the

observation of the intimate physical processes which lie at the

foundation of vital phenomena. For the physiologist this

perfection of the compound microscope had the same significance

that the, discovery of America had for the fifteenth-century

geographers--it promised a veritable world of utterly novel

revelations. Nor was the fulfilment of that promise long delayed.

Indeed, so numerous and so important were the discoveries now

made in the realm of minute anatomy that the rise of histology to

the rank of an independent science may be said to date from this

period. Hitherto, ever since the discovery of magnifying-glasses,

there had been here and there a man, such as Leuwenhoek or

Malpighi, gifted with exceptional vision, and perhaps unusually

happy in his conjectures, who made important contributions to the

knowledge of the minute structure of organic tissues; but now of

a sudden it became possible for the veriest tyro to confirm or

refute the laborious observations of these pioneers, while the

skilled observer could step easily beyond the barriers of vision

that hitherto were quite impassable. And so, naturally enough,

the physiologists of the fourth decade of the nineteenth century

rushed as eagerly into the new realm of the microscope as, for

example, their successors of to-day are exploring the realm of

the X-ray.

Lister himself, who had become an eager interrogator of the

instrument he had perfected, made many important discoveries, the

most notable being his final settlement of the long-mooted

question as to the true form of the red corpuscles of the human

blood. In reality, as everybody knows nowadays, these are

biconcave disks, but owing to their peculiar figure it is easily

possible to misinterpret the appearances they present when seen

through a poor lens, and though Dr. Thomas Young and various

other observers had come very near the truth regarding them,

unanimity of opinion was possible only after the verdict of the

perfected microscope was given.

These blood corpuscles are so infinitesimal in size that

something like five millions of them are found in each cubic

millimetre of the blood, yet they are isolated particles, each

having, so to speak, its own personality. This, of course, had

been known to microscopists since the days of the earliest

lenses. It had been noticed, too, by here and there an observer,

that certain of the solid tissues seemed to present something of

a granular texture, as if they, too, in their ultimate

constitution, were made up of particles. And now, as better and

better lenses were constructed, this idea gained ground

constantly, though for a time no one saw its full significance.

In the case of vegetable tissues, indeed, the fact that little

particles encased a membranous covering, and called cells, are

the ultimate visible units of structure had long been known. But

it was supposed that animal tissues differed radically from this

construction. The elementary particles of vegetables "were

regarded to a certain extent as individuals which composed the

entire plant, while, on the other hand, no such view was taken of

the elementary parts of animals."


In the year 1833 a further insight into the nature of the

ultimate particles of plants was gained through the observation

of the English microscopist Robert Brown, who, in the course of

his microscopic studies of the epidermis of orchids, discovered

in the cells "an opaque spot," which he named the nucleus.

Doubtless the same "spot" had been seen often enough before by

other observers, but Brown was the first to recognize it as a

component part of the vegetable cell and to give it a name.

"I shall conclude my observations on Orchideae," said Brown,

"with a notice of some points of their general structure, which

chiefly relate to the cellular tissue. In each cell of the

epidermis of a great part of this family, especially of those

with membranous leaves, a single circular areola, generally

somewhat more opaque than, the membrane of the cell, is

observable. This areola, which is more or less distinctly

granular, is slightly convex, and although it seems to be on the

surface is in reality covered by the outer lamina of the cell.

There is no regularity as to its place in the cell; it is not

unfrequently, however, central or nearly so.

"As only one areola belongs to each cell, and as in many cases

where it exists in the common cells of the epidermis, it is also

visible in the cutaneous glands or stomata, and in these is

always double--one being on each side of the limb--it is highly

probable that the cutaneous gland is in all cases composed of two

cells of peculiar form, the line of union being the longitudinal

axis of the disk or pore.

"This areola, or nucleus of the cell as perhaps it might be

termed, is not confined to the epidermis, being also found, not

only in the pubescence of the surface, particularly when jointed,

as in cypripedium, but in many cases in the parenchyma or

internal cells of the tissue, especially when these are free from

the deposition of granular matter.

"In the compressed cells of the epidermis the nucleus is in a

corresponding degree flattened; but in the internal tissue it is

often nearly spherical, more or less firmly adhering to one of

the walls, and projecting into the cavity of the cell. In this

state it may not unfrequently be found. in the substance of the

column and in that of the perianthium.

"The nucleus is manifest also in the tissue of the stigma, where

in accordance with the compression of the utriculi, it has an

intermediate form, being neither so much flattened as in the

epidermis nor so convex as it is in the internal tissue of the


"I may here remark that I am acquainted with one case of apparent

exception to the nucleus being solitary in each utriculus or

cell--namely, in Bletia Tankervilliae. In the utriculi of the

stigma of this plant, I have generally, though not always, found

a second areola apparently on the surface, and composed of much

larger granules than the ordinary nucleus, which is formed of

very minute granular matter, and seems to be deep seated.

"Mr. Bauer has represented the tissue of the stigma, in the

species of Bletia, both before and, as he believes, after

impregnation; and in the latter state the utriculi are marked

with from one to three areolae of similar appearance.

"The nucleus may even be supposed to exist in the pollen of this

family. In the early stages of its formation, at least a minute

areola is of ten visible in the simple grain, and in each of the

constituent parts of cells of the compound grain. But these

areolae may perhaps rather be considered as merely the points of

production of the tubes.

"This nucleus of the cell is not confined to orchideae, but is

equally manifest in many other monocotyledonous families; and I

have even found it, hitherto however in very few cases, in the

epidermis of dicotyledonous plants; though in this primary

division it may perhaps be said to exist in the early stages of

development of the pollen. Among monocotyledons, the orders in

which it is most remarkable are Liliaceae, Hemerocallideae,

Asphodeleae, Irideae, and Commelineae.

"In some plants belonging to this last-mentioned family,

especially in Tradascantia virginica, and several nearly related

species, it is uncommonly distinct, not in the epidermis and in

the jointed hairs of the filaments, but in the tissue of the

stigma, in the cells of the ovulum even before impregnation, and

in all the stages of formation of the grains of pollen, the

evolution of which is so remarkable in tradascantia.

"The few indications of the presence of this nucleus, or areola,

that I have hitherto met with in the publications of botanists

are chiefly in some figures of epidermis, in the recent works of

Meyen and Purkinje, and in one case, in M. Adolphe Broigniart's

memoir on the structure of leaves. But so little importance

seems to be attached to it that the appearance is not always

referred to in the explanations of the figures in which it is

represented. Mr. Bauer, however, who has also figured it in the

utriculi of the stigma of Bletia Tankervilliae has more

particularly noticed it, and seems to consider it as only visible

after impregnation."[2]


That this newly recognized structure must be important in the

economy of the cell was recognized by Brown himself, and by the

celebrated German Meyen, who dealt with it in his work on

vegetable physiology, published not long afterwards; but it

remained for another German, the professor of botany in the

University of Jena, Dr. M. J. Schleiden, to bring the nucleus to

popular attention, and to assert its all-importance in the

economy of the cell.

Schleiden freely acknowledged his indebtedness to Brown for first

knowledge of the nucleus, but he soon carried his studies of that

structure far beyond those of its discoverer. He came to believe

that the nucleus is really the most important portion of the

cell, in that it is the original structure from which the

remainder of the cell is developed. Hence he named it the

cytoblast. He outlined his views in an epochal paper published

in Muller's Archives in 1838, under title of "Beitrage zur

Phytogenesis." This paper is in itself of value, yet the most

important outgrowth of Schleiden's observations of the nucleus

did not spring from his own labors, but from those of a friend to

whom he mentioned his discoveries the year previous to their

publication. This friend was Dr. Theodor Schwann, professor of

physiology in the University of Louvain.

At the moment when these observations were communicated to him

Schwann was puzzling over certain details of animal histology

which he could not clearly explain. His great teacher, Johannes

Muller, had called attention to the strange resemblance to

vegetable cells shown by certain cells of the chorda dorsalis

(the embryonic cord from which the spinal column is developed),

and Schwann himself had discovered a corresponding similarity in

the branchial cartilage of a tadpole. Then, too, the researches

of Friedrich Henle had shown that the particles that make up the

epidermis of animals are very cell-like in appearance. Indeed,

the cell-like character of certain animal tissues had come to be

matter of common note among students of minute anatomy. Schwann

felt that this similarity could not be mere coincidence, but he

had gained no clew to further insight until Schleiden called his

attention to the nucleus. Then at once he reasoned that if there

really is the correspondence between vegetable and animal tissues

that he suspected, and if the nucleus is so important in the

vegetable cell as Schleiden believed, the nucleus should also be

found in the ultimate particles of animal tissues.

Schwann's researches soon showed the entire correctness of this

assumption. A closer study of animal tissues under the microscope

showed, particularly in the case of embryonic tissues, that

"opaque spots" such as Schleiden described are really to be found

there in abundance--forming, indeed, a most characteristic phase

of the structure. The location of these nuclei at comparatively

regular intervals suggested that they are found in definite

compartments of the tissue, as Schleiden had shown to be the case

with vegetables; indeed, the walls that separated such cell-like

compartments one from another were in some cases visible.

Particularly was this found to be the case with embryonic

tissues, and the study of these soon convinced Schwann that his

original surmise had been correct, and that all animal tissues

are in their incipiency composed of particles not unlike the

ultimate particles of vegetables in short, of what the botanists

termed cells. Adopting this name, Schwann propounded what soon

became famous as his cell theory, under title of Mikroskopische

Untersuchungen uber die Ubereinstimmung in der Structur und dent

Wachsthum der Thiere und Pflanzen. So expeditious had been his

work that this book was published early in 1839, only a few

months after the appearance of Schleiden's paper.

As the title suggests, the main idea that actuated Schwann was to

unify vegetable and animal tissues. Accepting cell-structure as

the basis of all vegetable tissues, he sought to show that the

same is true of animal tissues, all the seeming diversities of

fibre being but the alteration and development of what were

originally simple cells. And by cell Schwann meant, as did

Schleiden also, what the word ordinarily implies--a cavity walled

in on all sides. He conceived that the ultimate constituents of

all tissues were really such minute cavities, the most important

part of which was the cell wall, with its associated nucleus. He

knew, indeed, that the cell might be filled with fluid contents,

but he regarded these as relatively subordinate in importance to

the wall itself. This, however, did not apply to the nucleus,

which was supposed to lie against the cell wall and in the

beginning to generate it. Subsequently the wall might grow so

rapidly as to dissociate itself from its contents, thus becoming

a hollow bubble or true cell; but the nucleus, as long as it

lasted, was supposed to continue in contact with the cell wall.

Schleiden had even supposed the nucleus to be a constituent part

of the wall, sometimes lying enclosed between two layers of its

substance, and Schwann quoted this view with seeming approval.

Schwann believed, however, that in the mature cell the nucleus

ceased to be functional and disappeared.

The main thesis as to the similarity of development of vegetable

and animal tissues and the cellular nature of the ultimate

constitution of both was supported by a mass of carefully

gathered evidence which a multitude of microscopists at once

confirmed, so Schwann's work became a classic almost from the

moment of its publication. Of course various other workers at

once disputed Schwann's claim to priority of discovery, in

particular the English microscopist Valentin, who asserted, not

without some show of justice, that he was working closely along

the same lines. Put so, for that matter, were numerous others,

as Henle, Turpin, Du-mortier, Purkinje, and Muller, all of whom

Schwann himself had quoted. Moreover, there were various

physiologists who earlier than any of these had foreshadowed the

cell theory--notably Kaspar Friedrich Wolff, towards the close of

the previous century, and Treviranus about 1807, But, as we have

seen in so many other departments of science, it is one thing to

foreshadow a discovery, it is quite another to give it full

expression and make it germinal of other discoveries. And when

Schwann put forward the explicit claim that "there is one

universal principle of development for the elementary parts, of

organisms, however different, and this principle is the formation

of cells," he enunciated a doctrine which was for all practical

purposes absolutely new and opened up a novel field for the

microscopist to enter. A most important era in physiology dates

from the publication of his book in 1839.


That Schwann should have gone to embryonic tissues for the

establishment of his ideas was no doubt due very largely to the

influence of the great Russian Karl Ernst von Baer, who about ten

years earlier had published the first part of his celebrated work

on embryology, and whose ideas were rapidly gaining ground,

thanks largely to the advocacy of a few men, notably Johannes

Muller, in Germany, and William B. Carpenter, in England, and to

the fact that the improved microscope had made minute anatomy

popular. Schwann's researches made it plain that the best field

for the study of the animal cell is here, and a host of explorers

entered the field. The result of their observations was, in the

main, to confirm the claims of Schwann as to the universal

prevalence of the cell. The long-current idea that animal tissues

grow only as a sort of deposit from the blood-vessels was now

discarded, and the fact of so-called plantlike growth of animal

cells, for which Schwann contended, was universally accepted. Yet

the full measure of the affinity between the two classes of cells

was not for some time generally apprehended.

Indeed, since the substance that composes the cell walls of

plants is manifestly very different from the limiting membrane of

the animal cell, it was natural, so long as the, wall was

considered the most essential part of the structure, that the

divergence between the two classes of cells should seem very

pronounced. And for a time this was the conception of the matter

that was uniformly accepted. But as time went on many observers

had their attention called to the peculiar characteristics of the

contents of the cell, and were led to ask themselves whether

these might not be more important than had been supposed. In

particular, Dr. Hugo von Mohl, professor of botany in the

University of Tubingen, in the course of his exhaustive studies

of the vegetable cell, was impressed with the peculiar and

characteristic appearance of the cell contents. He observed

universally within the cell "an opaque, viscid fluid, having

granules intermingled in it," which made up the main substance of

the cell, and which particularly impressed him because under

certain conditions it could be seen to be actively in motion, its

parts separated into filamentous streams.

Von Mohl called attention to the fact that this motion of the

cell contents had been observed as long ago as 1774 by

Bonaventura Corti, and rediscovered in 1807 by Treviranus, and

that these observers had described the phenomenon under the "most

unsuitable name of 'rotation of the cell sap.' Von Mohl

recognized that the streaming substance was something quite

different from sap. He asserted that the nucleus of the cell lies

within this substance and not attached to the cell wall as

Schleiden had contended. He saw, too, that the chlorophyl

granules, and all other of the cell contents, are incorporated

with the "opaque, viscid fluid," and in 1846 he had become so

impressed with the importance of this universal cell substance

that be gave it the name of protoplasm. Yet in so doing he had no

intention of subordinating the cell wall. The fact that Payen, in

1844, had demonstrated that the cell walls of all vegetables,

high or low, are composed largely of one substance, cellulose,

tended to strengthen the position of the cell wall as the really

essential structure, of which the protoplasmic contents were only

subsidiary products.

Meantime, however, the students of animal histology were more and

more impressed with the seeming preponderance of cell contents

over cell walls in the tissues they studied. They, too, found

the cell to be filled with a viscid, slimy fluid capable of

motion. To this Dujardin gave the name of sarcode. Presently it

came to be known, through the labors of Kolliker, Nageli,

Bischoff, and various others, that there are numerous lower forms

of animal life which seem to be composed of this sarcode, without

any cell wall whatever. The same thing seemed to be true of

certain cells of higher organisms, as the blood corpuscles.

Particularly in the case of cells that change their shape

markedly, moving about in consequence of the streaming of their

sarcode, did it seem certain that no cell wall is present, or

that, if present, its role must be insignificant.

And so histologists came to question whether, after all, the cell

contents rather than the enclosing wall must not be the really

essential structure, and the weight of increasing observations

finally left no escape from the conclusion that such is really

the case. But attention being thus focalized on the cell

contents, it was at once apparent that there is a far closer

similarity between the ultimate particles of vegetables and those

of animals than had been supposed. Cellulose and animal membrane

being now regarded as more by-products, the way was clear for the

recognition of the fact that vegetable protoplasm and animal

sarcode are marvellously similar in appearance and general

properties. The closer the observation the more striking seemed

this similarity; and finally, about 1860, it was demonstrated by

Heinrich de Bary and by Max Schultze that the two are to all

intents and purposes identical. Even earlier Remak had reached a

similar conclusion, and applied Von Mohl's word protoplasm to

animal cell contents, and now this application soon became

universal. Thenceforth this protoplasm was to assume the utmost

importance in the physiological world, being recognized as the

universal "physical basis of life," vegetable and animal alike.

This amounted to the logical extension and culmination of

Schwann's doctrine as to the similarity of development of the two

animate kingdoms. Yet at the, same time it was in effect the

banishment of the cell that Schwann had defined. The word cell

was retained, it is true, but it no longer signified a minute

cavity. It now implied, as Schultze defined it, "a small mass of

protoplasm endowed with the attributes of life." This definition

was destined presently to meet with yet another modification, as

we shall see; but the conception of the protoplasmic mass as the

essential ultimate structure, which might or might not surround

itself with a protective covering, was a permanent addition to

physiological knowledge. The earlier idea had, in effect,

declared the shell the most important part of the egg; this

developed view assigned to the yolk its true position.

In one other important regard the theory of Schleiden and Schwann

now became modified. This referred to the origin of the cell.

Schwann had regarded cell growth as a kind of crystallization,

beginning with the deposit of a nucleus about a granule in the

intercellular substance--the cytoblastema, as Schleiden called

it. But Von Mohl, as early as 1835, had called attention to the

formation of new vegetable cells through the division of a

pre-existing cell. Ehrenberg, another high authority of the time,

contended that no such division occurs, and the matter was still

in dispute when Schleiden came forward with his discovery of

so-called free cell-formation within the parent cell, and this

for a long time diverted attention from the process of division

which Von Mohl had described. All manner of schemes of

cell-formation were put forward during the ensuing years by a

multitude of observers, and gained currency notwithstanding Von

Mohl's reiterated contention that there are really but two ways

in which the formation of new cells takes place--namely, "first,

through division of older cells; secondly, through the formation

of secondary cells lying free in the cavity of a cell."

But gradually the researches of such accurate observers as Unger,

Nageli, Kolliker, Reichart, and Remak tended to confirm the

opinion of Von Mohl that cells spring only from cells, and

finally Rudolf Virchow brought the matter to demonstration about

1860. His Omnis cellula e cellula became from that time one of

the accepted data of physiology. This was supplemented a little

later by Fleming's Omnis nucleus e nucleo, when still more

refined methods of observation had shown that the part of the

cell which always first undergoes change preparatory to new

cell-formation is the all-essential nucleus. Thus the nucleus was

restored to the important position which Schwann and Schleiden

had given it, but with greatly altered significance. Instead of

being a structure generated de novo from non-cellular substance,

and disappearing as soon as its function of cell-formation was

accomplished, the nucleus was now known as the central and

permanent feature of every cell, indestructible while the cell

lives, itself the division-product of a pre-existing nucleus, and

the parent, by division of its substance, of other generations of

nuclei. The word cell received a final definition as "a small

mass of protoplasm supplied with a nucleus."

In this widened and culminating general view of the cell theory

it became clear that every animate organism, animal or vegetable,

is but a cluster of nucleated cells, all of which, in each

individual case, are the direct descendants of a single

primordial cell of the ovum. In the developed individuals of

higher organisms the successive generations of cells become

marvellously diversified in form and in specific functions; there

is a wonderful division of labor, special functions being chiefly

relegated to definite groups of cells; but from first to last

there is no function developed that is not present, in a

primitive way, in every cell, however isolated; nor does the

developed cell, however specialized, ever forget altogether any

one of its primordial functions or capacities. All physiology,

then, properly interpreted, becomes merely a study of cellular

activities; and the development of the cell theory takes its

place as the great central generalization in physiology of the

nineteenth century. Something of the later developments of this

theory we shall see in another connection.


Just at the time when the microscope was opening up the paths

that were to lead to the wonderful cell theory, another novel

line of interrogation of the living organism was being put

forward by a different set of observers. Two great schools of

physiological chemistry had arisen--one under guidance of Liebig

and Wohler, in Germany, the other dominated by the great French

master Jean Baptiste Dumas. Liebig had at one time contemplated

the study of medicine, and Dumas had achieved distinction in

connection with Prevost, at Geneva, in the field of pure

physiology before he turned his attention especially to

chemistry. Both these masters, therefore, and Wohler as well,

found absorbing interest in those phases of chemistry that have

to do with the functions of living tissues; and it was largely

through their efforts and the labors of their followers that the

prevalent idea that vital processes are dominated by unique laws

was discarded and physiology was brought within the recognized

province of the chemist. So at about the time when the microscope

had taught that the cell is the really essential structure of the

living organism, the chemists had come to understand that every

function of the organism is really the expression of a chemical

change--that each cell is, in short, a miniature chemical

laboratory. And it was this combined point of view of anatomist

and chemist, this union of hitherto dissociated forces, that made

possible the inroads into the unexplored fields of physiology

that were effected towards the middle of the nineteenth century.

One of the first subjects reinvestigated and brought to proximal

solution was the long-mooted question of the digestion of foods.

Spallanzani and Hunter had shown in the previous century that

digestion is in some sort a solution of foods; but little advance

was made upon their work until 1824, when Prout detected the

presence of hydrochloric acid in the gastric juice. A decade

later Sprott and Boyd detected the existence of peculiar glands

in the gastric mucous membrane; and Cagniard la Tour and Schwann

independently discovered that the really active principle of the

gastric juice is a substance which was named pepsin, and which

was shown by Schwann to be active in the presence of hydrochloric


Almost coincidently, in 1836, it was discovered by Purkinje and

Pappenheim that another organ than the stomach--namely, the

pancreas--has a share in digestion, and in the course of the

ensuing decade it came to be known, through the efforts of

Eberle, Valentin, and Claude Bernard, that this organ is

all-important in the digestion of starchy and fatty foods. It was

found, too, that the liver and the intestinal glands have each an

important share in the work of preparing foods for absorption, as

also has the saliva--that, in short, a coalition of forces is

necessary for the digestion of all ordinary foods taken into the


And the chemists soon discovered that in each one of the

essential digestive juices there is at least one substance having

certain resemblances to pepsin, though acting on different kinds

of food. The point of resemblance between all these essential

digestive agents is that each has the remarkable property of

acting on relatively enormous quantities of the substance which

it can digest without itself being destroyed or apparently even

altered. In virtue of this strange property, pepsin and the

allied substances were spoken of as ferments, but more recently

it is customary to distinguish them from such organized ferments

as yeast by designating them enzymes. The isolation of these

enzymes, and an appreciation of their mode of action, mark a long

step towards the solution of the riddle of digestion, but it must

be added that we are still quite in the dark as to the real

ultimate nature of their strange activity.

In a comprehensive view, the digestive organs, taken as a whole,

are a gateway between the outside world and the more intimate

cells of the organism. Another equally important gateway is

furnished by the lungs, and here also there was much obscurity

about the exact method of functioning at the time of the revival

of physiological chemistry. That oxygen is consumed and carbonic

acid given off during respiration the chemists of the age of

Priestley and Lavoisier had indeed made clear, but the mistaken

notion prevailed that it was in the lungs themselves that the

important burning of fuel occurs, of which carbonic acid is a

chief product. But now that attention had been called to the

importance of the ultimate cell, this misconception could not

long hold its ground, and as early as 1842 Liebig, in the course

of his studies of animal heat, became convinced that it is not in

the lungs, but in the ultimate tissues to which they are

tributary, that the true consumption of fuel takes place.

Reviving Lavoisier's idea, with modifications and additions,

Liebig contended, and in the face of opposition finally

demonstrated, that the source of animal heat is really the

consumption of the fuel taken in through the stomach and the

lungs. He showed that all the activities of life are really the

product of energy liberated solely through destructive processes,

amounting, broadly speaking, to combustion occurring in the

ultimate cells of the organism. Here is his argument:


"The oxygen taken into the system is taken out again in the same

forms, whether in summer or in winter; hence we expire more

carbon in cold weather, and when the barometer is high, than we

do in warm weather; and we must consume more or less carbon in

our food in the same proportion; in Sweden more than in Sicily;

and in our more temperate climate a full eighth more in winter

than in summer.

"Even when we consume equal weights of food in cold and warm

countries, infinite wisdom has so arranged that the articles of

food in different climates are most unequal in the proportion of

carbon they contain. The fruits on which the natives of the South

prefer to feed do not in the fresh state contain more than twelve

per cent. of carbon, while the blubber and train-oil used by the

inhabitants of the arctic regions contain from sixty-six to

eighty per cent. of carbon.

"It is no difficult matter, in warm climates, to study moderation

in eating, and men can bear hunger for a long time under the

equator; but cold and hunger united very soon exhaust the body.

"The mutual action between the elements of the food and the

oxygen conveyed by the circulation of the blood to every part of

the body is the source of animal heat.

"All living creatures whose existence depends on the absorption

of oxygen possess within themselves a source of heat independent

of surrounding objects.

"This truth applies to all animals, and extends besides to the

germination of seeds, to the flowering of plants, and to the

maturation of fruits. It is only in those parts of the body to

which arterial blood, and with it the oxygen absorbed in

respiration, is conveyed that heat is produced. Hair, wool, or

feathers do not possess an elevated temperature. This high

temperature of the animal body, or, as it may be called,

disengagement of heat, is uniformly and under all circumstances

the result of the combination of combustible substance with


"In whatever way carbon may combine with oxygen, the act of

combination cannot take place without the disengagement of heat.

It is a matter of indifference whether the combination takes

place rapidly or slowly, at a high or at a low temperature; the

amount of heat liberated is a constant quantity. The carbon of

the food, which is converted into carbonic acid within the body,

must give out exactly as much heat as if it had been directly

burned in the air or in oxygen gas; the only difference is that

the amount of heat produced is diffused over unequal times. In

oxygen the combustion is more rapid and the heat more intense; in

air it is slower, the temperature is not so high, but it

continues longer.

"It is obvious that the amount of heat liberated must increase or

diminish with the amount of oxygen introduced in equal times by

respiration. Those animals which respire frequently, and

consequently consume much oxygen, possess a higher temperature

than others which, with a body of equal size to be heated, take

into the system less oxygen. The temperature of a child (102

degrees) is higher than that of an adult (99.5 degrees). That of

birds (104 to 105.4 degrees) is higher than that of quadrupeds

(98.5 to 100.4 degrees), or than that of fishes or amphibia,

whose proper temperature is from 3.7 to 2.6 degrees higher than

that of the medium in which they live. All animals, strictly

speaking, are warm-blooded; but in those only which possess lungs

is the temperature of the body independent of the surrounding


"The most trustworthy observations prove that in all climates, in

the temperate zones as well as at the equator or the poles, the

temperature of the body in man, and of what are commonly called

warm-blooded animals, is invariably the same; yet how different

are the circumstances in which they live.

"The animal body is a heated mass, which bears the same relation

to surrounding objects as any other heated mass. It receives heat

when the surrounding objects are hotter, it loses heat when they

are colder than itself. We know that the rapidity of cooling

increases with the difference between the heated body and that of

the surrounding medium--that is, the colder the surrounding

medium the shorter the time required for the cooling of the

heated body. How unequal, then, must be the loss of heat of a man

at Palermo, where the actual temperature is nearly equal to that

of the body, and in the polar regions, where the external

temperature is from 70 to 90 degrees lower.

"Yet notwithstanding this extremely unequal loss of heat,

experience has shown that the blood of an inhabitant of the

arctic circle has a temperature as high as that of the native of

the South, who lives in so different a medium. This fact, when

its true significance is perceived, proves that the heat given

off to the surrounding medium is restored within the body with

great rapidity. This compensation takes place more rapidly in

winter than in summer, at the pole than at the equator.

"Now in different climates the quantity of oxygen introduced into

the system of respiration, as has been already shown, varies

according to the temperature of the external air; the quantity of

inspired oxygen increases with the loss of heat by external

cooling, and the quantity of carbon or hydrogen necessary to

combine with this oxygen must be increased in like ratio. It is

evident that the supply of heat lost by cooling is effected by

the mutual action of the elements of the food and the inspired

oxygen, which combine together. To make use of a familiar, but

not on that account a less just illustration, the animal body

acts, in this respect, as a furnace, which we supply with fuel.

It signifies nothing what intermediate forms food may assume,

what changes it may undergo in the body, the last change is

uniformly the conversion of carbon into carbonic acid and of its

hydrogen into water; the unassimilated nitrogen of the food,

along with the unburned or unoxidized carbon, is expelled in the

excretions. In order to keep up in a furnace a constant

temperature, we must vary the supply of fuel according to the

external temperature--that is, according to the supply of oxygen.

"In the animal body the food is the fuel; with a proper supply of

oxygen we obtain the heat given out during its oxidation or



Further researches showed that the carriers of oxygen, from the

time of its absorption in the lungs till its liberation in the

ultimate tissues, are the red corpuscles, whose function had been

supposed to be the mechanical one of mixing of the blood. It

transpired that the red corpuscles are composed chiefly of a

substance which Kuhne first isolated in crystalline form in 1865,

and which was named haemoglobin--a substance which has a

marvellous affinity for oxygen, seizing on it eagerly at the

lungs vet giving it up with equal readiness when coursing among

the remote cells of the body. When freighted with oxygen it

becomes oxyhaemoglobin and is red in color; when freed from its

oxygen it takes a purple hue; hence the widely different

appearance of arterial and venous blood, which so puzzled the

early physiologists.

This proof of the vitally important role played by the red-blood

corpuscles led, naturally, to renewed studies of these

infinitesimal bodies. It was found that they may vary greatly in

number at different periods in the life of the same individual,

proving that they may be both developed and destroyed in the

adult organism. Indeed, extended observations left no reason to

doubt that the process of corpuscle formation and destruction may

be a perfectly normal one--that, in short, every red-blood

corpuscle runs its course and dies like any more elaborate

organism. They are formed constantly in the red marrow of bones,

and are destroyed in the liver, where they contribute to the

formation of the coloring matter of the bile. Whether there are

other seats of such manufacture and destruction of the corpuscles

is not yet fully determined. Nor are histologists agreed as to

whether the red-blood corpuscles themselves are to be regarded as

true cells, or merely as fragments of cells budded out from a

true cell for a special purpose; but in either case there is not

the slightest doubt that the chief function of the red corpuscle

is to carry oxygen.

If the oxygen is taken to the ultimate cells before combining

with the combustibles it is to consume, it goes without saying

that these combustibles themselves must be carried there also.

Nor could it be in doubt that the chiefest of these ultimate

tissues, as regards, quantity of fuel required, are the muscles.

A general and comprehensive view of the organism includes, then,

digestive apparatus and lungs as the channels of fuel-supply;

blood and lymph channels as the transportation system; and muscle

cells, united into muscle fibres, as the consumption furnaces,

where fuel is burned and energy transformed and rendered

available for the purposes of the organism, supplemented by a set

of excretory organs, through which the waste products--the

ashes--are eliminated from the system.

But there remain, broadly speaking, two other sets of organs

whose size demonstrates their importance in the economy of the

organism, yet whose functions are not accounted for in this

synopsis. These are those glandlike organs, such as the spleen,

which have no ducts and produce no visible secretions, and the

nervous mechanism, whose central organs are the brain and spinal

cord. What offices do these sets of organs perform in the great

labor-specializing aggregation of cells which we call a living


As regards the ductless glands, the first clew to their function

was given when the great Frenchman Claude Bernard (the man of

whom his admirers loved to say, "He is not a physiologist merely;

he is physiology itself") discovered what is spoken of as the

glycogenic function of the liver. The liver itself, indeed, is

not a ductless organ, but the quantity of its biliary output

seems utterly disproportionate to its enormous size, particularly

when it is considered that in the case of the human species the

liver contains normally about one-fifth of all the blood in the

entire body. Bernard discovered that the blood undergoes a change

of composition in passing through the liver. The liver cells

(the peculiar forms of which had been described by Purkinje,

Henle, and Dutrochet about 1838) have the power to convert

certain of the substances that come to them into a starchlike

compound called glycogen, and to store this substance away till

it is needed by the organism. This capacity of the liver cells

is quite independent of the bile-making power of the same cells;

hence the discovery of this glycogenic function showed that an

organ may have more than one pronounced and important specific

function. But its chief importance was in giving a clew to those

intermediate processes between digestion and final assimilation

that are now known to be of such vital significance in the

economy of the organism.

In the forty odd years that have elapsed since this pioneer

observation of Bernard, numerous facts have come to light showing

the extreme importance of such intermediate alterations of

food-supplies in the blood as that performed by the liver. It has

been shown that the pancreas, the spleen, the thyroid gland, the

suprarenal capsules are absolutely essential, each in its own

way, to the health of the organism, through metabolic changes

which they alone seem capable of performing; and it is suspected

that various other tissues, including even the muscles

themselves, have somewhat similar metabolic capacities in

addition to their recognized functions. But so extremely

intricate is the chemistry of the substances involved that in no

single case has the exact nature of the metabolisms wrought by

these organs been fully made out. Each is in its way a chemical

laboratory indispensable to the right conduct of the organism,

but the precise nature of its operations remains inscrutable. The

vast importance of the operations of these intermediate organs is


A consideration of the functions of that other set of organs

known collectively as the nervous system is reserved for a later




When Coleridge said of Humphry Davy that he might have been the

greatest poet of his time had he not chosen rather to be the

greatest chemist, it is possible that the enthusiasm of the

friend outweighed the caution of the critic. But however that

may be, it is beyond dispute that the man who actually was the

greatest poet of that time might easily have taken the very

highest rank as a scientist had not the muse distracted his

attention. Indeed, despite these distractions, Johann Wolfgang

von Goethe achieved successes in the field of pure science that

would insure permanent recognition for his name had he never

written a stanza of poetry. Such is the versatility that marks

the highest genius.

It was in 1790 that Goethe published the work that laid the

foundations of his scientific reputation--the work on the

Metamorphoses of Plants, in which he advanced the novel doctrine

that all parts of the flower are modified or metamorphosed


"Every one who observes the growth of plants, even

superficially," wrote Goethe, "will notice that certain external

parts of them become transformed at times and go over into the

forms of the contiguous parts, now completely, now to a greater

or less degree. Thus, for example, the single flower is

transformed into a double one when, instead of stamens, petals

are developed, which are either exactly like the other petals of

the corolla in form, and color or else still bear visible signs

of their origin.

"When we observe that it is possible for a plant in this way to

take a step backward, we shall give so much the more heed to the

regular course of nature and learn the laws of transformation

according to which she produces one part through another, and

displays the most varying forms through the modification of one

single organ.

"Let us first direct our attention to the plant at the moment

when it develops out of the seed-kernel. The first organs of its

upward growth are known by the name of cotyledons; they have also

been called seed-leaves.

"They often appear shapeless, filled with new matter, and are

just as thick as they are broad. Their vessels are

unrecognizable and are hardly to be distinguished from the mass

of the whole; they bear almost no resemblance to a leaf, and we

could easily be misled into regarding them as special organs.

Occasionally, however, they appear as real leaves, their vessels

are capable of the most minute development, their similarity to

the following leaves does not permit us to take them for special

organs, but we recognize them instead to be the first leaves of

the stalk.

"The cotyledons are mostly double, and there is an observation to

be made here which will appear still more important as we

proceed--that is, that the leaves of the first node are often

paired, even when the following leaves of the stalk stand

alternately upon it. Here we see an approximation and a joining

of parts which nature afterwards separates and places at a

distance from one another. It is still more remarkable when the

cotyledons take the form of many little leaves gathered about an

axis, and the stalk which grows gradually from their midst

produces the following leaves arranged around it singly in a

whorl. This may be observed very exactly in the growth of the

pinus species. Here a corolla of needles forms at the same time a

calyx, and we shall have occasion to remember the present case in

connection with similar phenomena later.

"On the other hand, we observe that even the cotyledons which are

most like a leaf when compared with the following leaves of the

stalk are always more undeveloped or less developed. This is

chiefly noticeable in their margin which is extremely simple and

shows few traces of indentation.

"A few or many of the next following leaves are often already

present in the seed, and lie enclosed between the cotyledons; in

their folded state they are known by the name of plumules. Their

form, as compared with the cotyledons and the following leaves,

varies in different plants. Their chief point of variance,

however, from the cotyledons is that they are flat, delicate, and

formed like real leaves generally. They are wholly green, rest on

a visible node, and can no longer deny their relationship to the

following leaves of the stalk, to which, however, they are

usually still inferior, in so far as that their margin is not

completely developed.

"The further development, however, goes on ceaselessly in the

leaf, from node to node; its midrib is elongated, and more or

less additional ribs stretch out from this towards the sides. The

leaves now appear notched, deeply indented, or composed of

several small leaves, in which last case they seem to form

complete little branches. The date-palm furnishes a striking

example of such a successive transformation of the simplest leaf

form. A midrib is elongated through a succession of several

leaves, the single fan-shaped leaf becomes torn and diverted, and

a very complicated leaf is developed, which rivals a branch in


"The transition to inflorescence takes place more or less

rapidly. In the latter case we usually observe that the leaves of

the stalk loose their different external divisions, and, on the

other hand, spread out more or less in their lower parts where

they are attached to the stalk. If the transition takes place

rapidly, the stalk, suddenly become thinner and more elongated

since the node of the last-developed leaf, shoots up and collects

several leaves around an axis at its end.

"That the petals of the calyx are precisely the same organs which

have hitherto appeared as leaves on the stalk, but now stand

grouped about a common centre in an often very different form,

can, as it seems to me, be most clearly demonstrated. Already in

connection with the cotyledons above, we noticed a similar

working of nature. The first species, while they are developing

out of the seed-kernel, display a radiate crown of unmistakable

needles; and in the first childhood of these plants we see

already indicated that force of nature whereby when they are

older their flowering and fruit-giving state will be produced.

"We see this force of nature, which collects several leaves

around an axis, produce a still closer union and make these

approximated, modified leaves still more unrecognizable by

joining them together either wholly or partially. The

bell-shaped or so-called one-petalled calices represent these

cloudy connected leaves, which, being more or less indented from

above, or divided, plainly show their origin.

"We can observe the transition from the calyx to the corolla in

more than one instance, for, although the color of the calyx is

still usually green, and like the color of the leaves of the

stalk, it nevertheless often varies in one or another of its

parts--at the tips, the margins, the back, or even, the inward

side--while the outer still remains on green.

"The relationship of the corolla to the leaves of the stalk is

shown in more than one way, since on the stalks of some plants

appear leaves which are already more or less colored long before

they approach inflorescence; others are fully colored when near

inflorescence. Nature also goes over at once to the corolla,

sometimes by skipping over the organs of the calyx, and in such a

case we likewise have an opportunity to observe that leaves of

the stalk become transformed into petals. Thus on the stalk of

tulips, for instance, there sometimes appears an almost

completely developed and colored petal. Even more remarkable is

the case when such a leaf, half green and half of it belonging to

the stalk, remains attached to the latter, while another colored

part is raised with the corolla, and the leaf is thus torn in


"The relationship between the petals and stamens is very close.

In some instances nature makes the transition regular--e.g.,

among the Canna and several plants of the same family. A true,

little-modified petal is drawn together on its upper margin, and

produces a pollen sac, while the rest of the petal takes the

place of the stamen. In double flowers we can observe this

transition in all its stages. In several kinds of roses, within

the fully developed and colored petals there appear other ones

which are drawn together in the middle or on the side. This

drawing together is produced by a small weal, which appears as a

more or less complete pollen sac, and in the same proportion the

leaf approaches the simple form of a stamen.

"The pistil in many cases looks almost like a stamen without

anthers, and the relationship between the formation of the two is

much closer than between the other parts. In retrograde fashion

nature often produces cases where the style and stigma (Narben)

become retransformed into petals--that is, the Ranunculus

Asiaticus becomes double by transforming the stigma and style of

the fruit-receptacle into real petals, while the stamens are

often found unchanged immediately behind the corolla.

"In the seed receptacles, in spite of their formation, of their

special object, and of their method of being joined together, we

cannot fail to recognize the leaf form. Thus, for instance, the

pod would be a simple leaf folded and grown together on its

margin; the siliqua would consist of more leaves folded over

another; the compound receptacles would be explained as being

several leaves which, being united above one centre, keep their

inward parts separate and are joined on their margins. We can

convince ourselves of this by actual sight when such composite

capsules fall apart after becoming ripe, because then every part

displays an opened pod."[1]

The theory thus elaborated of the metamorphosis of parts was

presently given greater generality through extension to the

animal kingdom, in the doctrine which Goethe and Oken advanced

independently, that the vertebrate skull is essentially a

modified and developed vertebra. These were conceptions worthy of

a poet--impossible, indeed, for any mind that had not the poetic

faculty of correlation. But in this case the poet's vision was

prophetic of a future view of the most prosaic science. The

doctrine of metamorphosis of parts soon came to be regarded as of

fundamental importance.

But the doctrine had implications that few of its early advocates

realized. If all the parts of a flower--sepal, petal, stamen,

pistil, with their countless deviations of contour and color--are

but modifications of the leaf, such modification implies a

marvellous differentiation and development. To assert that a

stamen is a metamorphosed leaf means, if it means anything, that

in the long sweep of time the leaf has by slow or sudden

gradations changed its character through successive generations,

until the offspring, so to speak, of a true leaf has become a

stamen. But if such a metamorphosis as this is possible--if the

seemingly wide gap between leaf and stamen may be spanned by the

modification of a line of organisms--where does the possibility

of modification of organic type find its bounds? Why may not the

modification of parts go on along devious lines until the remote

descendants of an organism are utterly unlike that organism? Why

may we not thus account for the development of various species of

beings all sprung from one parent stock? That, too, is a poet's

dream; but is it only a dream? Goethe thought not. Out of his

studies of metamorphosis of parts there grew in his mind the

belief that the multitudinous species of plants and animals about

us have been evolved from fewer and fewer earlier parent types,

like twigs of a giant tree drawing their nurture from the same

primal root. It was a bold and revolutionary thought, and the

world regarded it as but the vagary of a poet.


Just at the time when this thought was taking form in Goethe's

brain, the same idea was germinating in the mind of another

philosopher, an Englishman of international fame, Dr. Erasmus

Darwin, who, while he lived, enjoyed the widest popularity as a

poet, the rhymed couplets of his Botanic Garden being quoted

everywhere with admiration. And posterity repudiating the verse

which makes the body of the book, yet grants permanent value to

the book itself, because, forsooth, its copious explanatory

foot-notes furnish an outline of the status of almost every

department of science of the time.

But even though he lacked the highest art of the versifier,

Darwin had, beyond peradventure, the imagination of a poet

coupled with profound scientific knowledge; and it was his poetic

insight, correlating organisms seemingly diverse in structure and

imbuing the lowliest flower with a vital personality, which led

him to suspect that there are no lines of demarcation in nature.

"Can it be," he queries, "that one form of organism has developed

from another; that different species are really but modified

descendants of one parent stock?" The alluring thought nestled

in his mind and was nurtured there, and grew in a fixed belief,

which was given fuller expression in his Zoonomia and in the

posthumous Temple of Nature.

Here is his rendering of the idea as versified in the Temple of


"Organic life beneath the shoreless waves
 Was born, and nursed in Ocean's pearly caves;
 First forms minute, unseen by spheric glass,
 Move on the mud, or pierce the watery mass;
 These, as successive generations bloom,
 New powers acquire and larger limbs assume;
 Whence countless groups of vegetation spring,
 And breathing realms of fin, and feet, and wing.

"Thus the tall Oak, the giant of the wood,
 Which bears Britannia's thunders on the flood;
 The Whale, unmeasured monster of the main;
 The lordly lion, monarch of the plain;
 The eagle, soaring in the realms of air,
 Whose eye, undazzled, drinks the solar glare;
 Imperious man, who rules the bestial crowd,
 Of language, reason, and reflection proud,
 With brow erect, who scorns this earthy sod,
 And styles himself the image of his God--
 Arose from rudiments of form and sense,
 An embryon point or microscopic ens!"[2]

Here, clearly enough, is the idea of evolution. But in that day

there was little proof forthcoming of its validity that could

satisfy any one but a poet, and when Erasmus Darwin died, in

1802, the idea of transmutation of species was still but an

unsubstantiated dream.

It was a dream, however, which was not confined to Goethe and

Darwin. Even earlier the idea had come more or less vaguely to

another great dreamer--and worker--of Germany, Immanuel Kant, and

to several great Frenchmen, including De Maillet, Maupertuis,

Robinet, and the famous naturalist Buffon--a man who had the

imagination of a poet, though his message was couched in most

artistic prose. Not long after the middle of the eighteenth

century Buffon had put forward the idea of transmutation of

species, and he reiterated it from time to time from then on till

his death in 1788. But the time was not yet ripe for the idea of

transmutation of species to burst its bonds.

And yet this idea, in a modified or undeveloped form, had taken

strange hold upon the generation that was upon the scene at the

close of the eighteenth century. Vast numbers of hitherto unknown

species of animals had been recently discovered in previously

unexplored regions of the globe, and the wise men were sorely

puzzled to account for the disposal of all of these at the time

of the deluge. It simplified matters greatly to suppose that

many existing species had been developed since the episode of the

ark by modification of the original pairs. The remoter bearings

of such a theory were overlooked for the time, and the idea that

American animals and birds, for example, were modified

descendants of Old-World forms--the jaguar of the leopard, the

puma of the lion, and so on--became a current belief with that

class of humanity who accept almost any statement as true that

harmonizes with their prejudices without realizing its


Thus it is recorded with eclat that the discovery of the close

proximity of America at the northwest with Asia removes all

difficulties as to the origin of the Occidental faunas and

floras, since Oriental species might easily have found their way

to America on the ice, and have been modified as we find them by

"the well-known influence of climate." And the persons who gave

expression to this idea never dreamed of its real significance.

In truth, here was the doctrine of evolution in a nutshell, and,

because its ultimate bearings were not clear, it seemed the most

natural of doctrines. But most of the persons who advanced it

would have turned from it aghast could they have realized its

import. As it was, however, only here and there a man like Buffon

reasoned far enough to inquire what might be the limits of such

assumed transmutation; and only here and there a Darwin or a

Goethe reached the conviction that there are no limits.


And even Goethe and Darwin had scarcely passed beyond that

tentative stage of conviction in which they held the thought of

transmutation of species as an ancillary belief not ready for

full exposition. There was one of their contemporaries, however,

who, holding the same conception, was moved to give it full

explication. This was the friend and disciple of Buffon, Jean

Baptiste de Lamarck. Possessed of the spirit of a poet and

philosopher, this great Frenchman had also the widest range of

technical knowledge, covering the entire field of animate nature.

The first half of his long life was devoted chiefly to botany, in

which he attained high distinction. Then, just at the beginning

of the nineteenth century, he turned to zoology, in particular to

the lower forms of animal life. Studying these lowly organisms,

existing and fossil, he was more and more impressed with the

gradations of form everywhere to be seen; the linking of diverse

families through intermediate ones; and in particular with the

predominance of low types of life in the earlier geological

strata. Called upon constantly to classify the various forms of

life in the course of his systematic writings, he found it more

and more difficult to draw sharp lines of demarcation, and at

last the suspicion long harbored grew into a settled conviction

that there is really no such thing as a species of organism in

nature; that "species" is a figment of the human imagination,

whereas in nature there are only individuals.

That certain sets of individuals are more like one another than

like other sets is of course patent, but this only means, said

Lamarck, that these similar groups have had comparatively recent

common ancestors, while dissimilar sets of beings are more

remotely related in consanguinity. But trace back the lines of

descent far enough, and all will culminate in one original stock.

All forms of life whatsoever are modified descendants of an

original organism. From lowest to highest, then, there is but one

race, one species, just as all the multitudinous branches and

twigs from one root are but one tree. For purposes of convenience

of description, we may divide organisms into orders, families,

genera, species, just as we divide a tree into root, trunk,

branches, twigs, leaves; but in the one case, as in the other,

the division is arbitrary and artificial.

In Philosophie Zoologique (1809), Lamarck first explicitly

formulated his ideas as to the transmutation of species, though

he had outlined them as early as 1801. In this memorable

publication not only did he state his belief more explicitly and

in fuller detail than the idea had been expressed by any

predecessor, but he took another long forward step, carrying him

far beyond all his forerunners except Darwin, in that he made an

attempt to explain the way in which the transmutation of species

had been brought about. The changes have been wrought, he said,

through the unceasing efforts of each organism to meet the needs

imposed upon it by its environment. Constant striving means the

constant use of certain organs. Thus a bird running by the

seashore is constantly tempted to wade deeper and deeper in

pursuit of food; its incessant efforts tend to develop its legs,

in accordance with the observed principle that the use of any

organ tends to strengthen and develop it. But such slightly

increased development of the legs is transmitted to the off

spring of the bird, which in turn develops its already improved

legs by its individual efforts, and transmits the improved

tendency. Generation after generation this is repeated, until the

sum of the infinitesimal variations, all in the same direction,

results in the production of the long-legged wading-bird. In a

similar way, through individual effort and transmitted tendency,

all the diversified organs of all creatures have been

developed--the fin of the fish, the wing of the bird, the hand of

man; nay, more, the fish itself, the bird, the man, even.

Collectively the organs make up the entire organism; and what is

true of the individual organs must be true also of their

ensemble, the living being.

Whatever might be thought of Lamarck's explanation of the cause

of transmutation--which really was that already suggested by

Erasmus Darwin--the idea of the evolution for which he contended

was but the logical extension of the conception that American

animals are the modified and degenerated descendants of European

animals. But people as a rule are little prone to follow ideas to

their logical conclusions, and in this case the conclusions were

so utterly opposed to the proximal bearings of the idea that the

whole thinking world repudiated them with acclaim. The very

persons who had most eagerly accepted the idea of transmutation

of European species into American species, and similar limited

variations through changed environment, because of the relief

thus given the otherwise overcrowded ark, were now foremost in

denouncing such an extension of the doctrine of transmutation as

Lamarck proposed.

And, for that matter, the leaders of the scientific world were

equally antagonistic to the Lamarckian hypothesis. Cuvier in

particular, once the pupil of Lamarck, but now his colleague, and

in authority more than his peer, stood out against the

transmutation doctrine with all his force. He argued for the

absolute fixity of species, bringing to bear the resources of a

mind which, as a mere repository of facts, perhaps never was

excelled. As a final and tangible proof of his position, he

brought forward the bodies of ibises that had been embalmed by

the ancient Egyptians, and showed by comparison that these do not

differ in the slightest particular from the ibises that visit the

Nile to-day.

Cuvier's reasoning has such great historical interest--being the

argument of the greatest opponent of evolution of that day--that

we quote it at some length.

"The following objections," he says, "have already been started

against my conclusions. Why may not the presently existing races

of mammiferous land quadrupeds be mere modifications or varieties

of those ancient races which we now find in the fossil state,

which modifications may have been produced by change of climate

and other local circumstances, and since raised to the present

excessive difference by the operations of similar causes during a

long period of ages?

"This objection may appear strong to those who believe in the

indefinite possibility of change of form in organized bodies, and

think that, during a succession of ages and by alterations of

habitudes, all the species may change into one another, or one of

them give birth to all the rest. Yet to these persons the

following answer may be given from their own system: If the

species have changed by degrees, as they assume, we ought to find

traces of this gradual modification. Thus, between the

palaeotherium and the species of our own day, we should be able

to discover some intermediate forms; and yet no such discovery

has ever been made. Since the bowels of the earth have not

preserved monuments of this strange genealogy, we have no right

to conclude that the ancient and now extinct species were as

permanent in their forms and characters as those which exist at

present; or, at least, that the catastrophe which destroyed them

did not leave sufficient time for the productions of the changes

that are alleged to have taken place.

"In order to reply to those naturalists who acknowledge that the

varieties of animals are restrained by nature within certain

limits, it would be necessary to examine how far these limits

extend. This is a very curious inquiry, and in itself exceedingly

interesting under a variety of relations, but has been hitherto

very little attended to. . . . . . . . .

Wild animals which subsist upon herbage feel the influence of

climate a little more extensively, because there is added to it

the influence of food, both in regard to its abundance and its

quality. Thus the elephants of one forest are larger than those

of another; their tusks also grow somewhat longer in places where

their food may happen to be more favorable for the production of

the substance of ivory. The same may take place in regard to the

horns of stags and reindeer. But let us examine two elephants,

the most dissimilar that can be conceived, we shall not discover

the smallest difference in the number and articulations of the

bones, the structure of the teeth, etc. . . . . . . . .

"Nature appears also to have guarded against the alterations of

species which might proceed from mixture of breeds by influencing

the various species of animals with mutual aversion from one

another. Hence all the cunning and all the force that man is able

to exert is necessary to accomplish such unions, even between

species that have the nearest resemblances. And when the mule

breeds that are thus produced by these forced conjunctions happen

to be fruitful, which is seldom the case, this fecundity never

continues beyond a few generations, and would not probably

proceed so far without a continuance of the same cares which

excited it at first. Thus we never see in a wild state

intermediate productions between the hare and the rabbit, between

the stag and the doe, or between the marten and the weasel. But

the power of man changes this established order, and continues to

produce all these intermixtures of which the various species are

susceptible, but which they would never produce if left to


"The degrees of these variations are proportional to the

intensity of the causes that produced them--namely, the slavery

or subjection under which those animals are to man. They do not

proceed far in half-domesticated species. In the cat, for

example, a softer or harsher fur, more brilliant or more varied

colors, greater or less size--these form the whole extent of

variety in the species; the skeleton of the cat of Angora differs

in no regular and constant circumstances from the wild-cat of

Europe. . . . . . . .

The most remarkable effects of the influence of man are produced

upon that animal which he has reduced most completely under

subjection. Dogs have been transported by mankind into every part

of the world and have submitted their action to his entire

direction. Regulated in their unions by the pleasure or caprice

of their masters, the almost endless varieties of dogs differ

from one another in color, in length, and abundance of hair,

which is sometimes entirely wanting; in their natural instincts;

in size, which varies in measure as one to five, mounting in some

instances to more than a hundredfold in bulk; in the form of

their ears, noses, and tails; in the relative length of their

legs; in the progressive development of the brain, in several of

the domesticated varieties occasioning alterations even in the

form of the head, some of them having long, slender muzzles with

a flat forehead, others having short muzzles with a forehead

convex, etc., insomuch that the apparent difference between a

mastiff and a water-spaniel and between a greyhound and a pugdog

are even more striking than between almost any of the wild

species of a genus. . . . . . . .

It follows from these observations that animals have certain

fixed and natural characters which resist the effects of every

kind of influence, whether proceeding from natural causes or

human interference; and we have not the smallest reason to

suspect that time has any more effect on them than climate.

"I am aware that some naturalists lay prodigious stress upon the

thousands which they can call into action by a dash of their

pens. In such matters, however, our only way of judging as to the

effects which may be produced by a long period of time is by

multiplying, as it were, such as are produced by a shorter time.

With this view I have endeavored to collect all the ancient

documents respecting the forms of animals; and there are none

equal to those furnished by the Egyptians, both in regard to

their antiquity and abundance. They have not only left us

representatives of animals, but even their identical bodies

embalmed and preserved in the catacombs.

"I have examined, with the greatest attention, the engraved

figures of quadrupeds and birds brought from Egypt to ancient

Rome, and all these figures, one with another, have a perfect

resemblance to their intended objects, such as they still are


"From all these established facts, there does not seem to be the

smallest foundation for supposing that the new genera which I

have discovered or established among extraneous fossils, such as

the paleoetherium, anoplotherium, megalonyx, mastodon,

pterodactylis, etc., have ever been the sources of any of our

present animals, which only differ so far as they are influenced

by time or climate. Even if it should prove true, which I am far

from believing to be the case, that the fossil elephants,

rhinoceroses, elks, and bears do not differ further from the

existing species of the same genera than the present races of

dogs differ among themselves, this would by no means be a

sufficient reason to conclude that they were of the same species;

since the races or varieties of dogs have been influenced by the

trammels of domesticity, which those other animals never did, and

indeed never could, experience."[3]

To Cuvier's argument from the fixity of Egyptian mummified birds

and animals, as above stated, Lamarck replied that this proved

nothing except that the ibis had become perfectly adapted to its

Egyptian surroundings in an early day, historically speaking, and

that the climatic and other conditions of the Nile Valley had not

since then changed. His theory, he alleged, provided for the

stability of species under fixed conditions quite as well as for

transmutation under varying conditions.

But, needless to say, the popular verdict lay with Cuvier; talent

won for the time against genius, and Lamarck was looked upon as

an impious visionary. His faith never wavered, however. He

believed that he had gained a true insight into the processes of

animate nature, and he reiterated his hypotheses over and over,

particularly in the introduction to his Histoire Naturelle des

Animaux sans Vertebres, in 1815, and in his Systeme des

Connaissances Positives de l'Homme, in 1820. He lived on till

1829, respected as a naturalist, but almost unrecognized as a



While the names of Darwin and Goethe, and in particular that of

Lamarck, must always stand out in high relief in this generation

as the exponents of the idea of transmutation of species, there

are a few others which must not be altogether overlooked in this

connection. Of these the most conspicuous is that of Gottfried

Reinhold Treviranus, a German naturalist physician, professor of

mathematics in the lyceum at Bremen.

It was an interesting coincidence that Treviranus should have

published the first volume of his Biologie, oder Philosophie der

lebenden Natur, in which his views on the transmutation of

species were expounded, in 1802, the same twelvemonth in which

Lamarck's first exposition of the same doctrine appeared in his

Recherches sur l'Organisation des Corps Vivants. It is singular,

too, that Lamarck, in his Hydrogelogie of the same date, should

independently have suggested "biology" as an appropriate word to

express the general science of living things. It is significant

of the tendency of thought of the time that the need of such a

unifying word should have presented itself simultaneously to

independent thinkers in different countries.

That same memorable year, Lorenz Oken, another philosophical

naturalist, professor in the University of Zurich, published the

preliminary outlines of his Philosophie der Natur, which, as

developed through later publications, outlined a theory of

spontaneous generation and of evolution of species. Thus it

appears that this idea was germinating in the minds of several of

the ablest men of the time during the first decade of our

century. But the singular result of their various explications

was to give sudden check to that undercurrent of thought which

for some time had been setting towards this conception. As soon

as it was made clear whither the concession that animals may be

changed by their environment must logically trend, the recoil

from the idea was instantaneous and fervid. Then for a generation

Cuvier was almost absolutely dominant, and his verdict was

generally considered final.

There was, indeed, one naturalist of authority in France who had

the hardihood to stand out against Cuvier and his school, and who

was in a position to gain a hearing, though by no means to divide

the following. This was Etienne Geoffroy Saint-Hilaire, the

famous author of the Philosophie Anatomique, and for many years

the colleague of Lamarck at the Jardin des Plantes. Like Goethe,

Geoffroy was pre-eminently an anatomist, and, like the great

German, he had early been impressed with the resemblances between

the analogous organs of different classes of beings. He

conceived the idea that an absolute unity of type prevails

throughout organic nature as regards each set of organs. Out of

this idea grew his gradually formed belief that similarity of

structure might imply identity of origin--that, in short, one

species of animal might have developed from another.

Geoffroy's grasp of this idea of transmutation was by no means so

complete as that of Lamarck, and he seems never to have fully

determined in his own mind just what might be the limits of such

development of species. Certainly he nowhere includes all organic

creatures in one line of descent, as Lamarck had done;

nevertheless, he held tenaciously to the truth as he saw it, in

open opposition to Cuvier, with whom he held a memorable debate

at the Academy of Sciences in 1830--the debate which so aroused

the interest and enthusiasm of Goethe, but which, in the opinion

of nearly every one else, resulted in crushing defeat for

Geoffrey, and brilliant, seemingly final, victory for the

advocate of special creation and the fixity of species.

With that all ardent controversy over the subject seemed to end,

and for just a quarter of a century to come there was published

but a single argument for transmutation of species which

attracted any general attention whatever. This oasis in a desert

generation was a little book called Vestiges of the Natural

History of Creation, which appeared anonymously in England in

1844, and which passed through numerous editions, and was the

subject of no end of abusive and derisive comment. This book, the

authorship of which remained for forty years a secret, is now

conceded to have been the work of Robert Chambers, the well-known

English author and publisher. The book itself is remarkable as

being an avowed and unequivocal exposition of a general doctrine

of evolution, its view being as radical and comprehensive as that

of Lamarck himself. But it was a resume of earlier efforts rather

than a new departure, to say nothing of its technical

shortcomings, which may best be illustrated by a quotation.

"The whole question," says Chambers, "stands thus: For the

theory of universal order--that is, order as presiding in both

the origin and administration of the world--we have the testimony

of a vast number of facts in nature, and this one in

addition--that whatever is left from the domain of ignorance, and

made undoubted matter of science, forms a new support to the same

doctrine. The opposite view, once predominant, has been

shrinking for ages into lesser space, and now maintains a footing

only in a few departments of nature which happen to be less

liable than others to a clear investigation. The chief of these,

if not almost the only one, is the origin of the organic

kingdoms. So long as this remains obscure, the supernatural will

have a certain hold upon enlightened persons. Should it ever be

cleared up in a way that leaves no doubt of a natural origin of

plants and animals, there must be a complete revolution in the

view which is generally taken of the relation of the Father of

our being.

"This prepares the way for a few remarks on the present state of

opinion with regard to the origin of organic nature. The great

difficulty here is the apparent determinateness of species. These

forms of life being apparently unchangeable, or at least always

showing a tendency to return to the character from which they

have diverged, the idea arises that there can have been no

progression from one to another; each must have taken its special

form, independently of other forms, directly from the appointment

of the Creator. The Edinburgh Review writer says, 'they were

created by the hand of God and adapted to the conditions of the

period.' Now it is, in the first place, not certain that species

constantly maintain a fixed character, for we have seen that what

were long considered as determinate species have been transmuted

into others. Passing, however, from this fact, as it is not

generally received among men of science, there remain some great

difficulties in connection with the idea of special creation.

First we should have to suppose, as pointed out in my former

volume, a most startling diversity of plan in the divine

workings, a great general plan or system of law in the leading

events of world-making, and a plan of minute, nice operation, and

special attention in some of the mere details of the process. The

discrepancy between the two conceptions is surely overpowering,

when we allow ourselves to see the whole matter in a steady and

rational light. There is, also, the striking fact of an

ascertained historical progress of plants and animals in the

order of their organization; marine and cellular plants and

invertebrated animals first, afterwards higher examples of both.

In an arbitrary system we had surely no reason to expect mammals

after reptiles; yet in this order they came. The writer in the

Edinburgh Review speaks of animals as coming in adaptation to

conditions, but this is only true in a limited sense. The groves

which formed the coal-beds might have been a fitting habitation

for reptiles, birds, and mammals, as such groves are at the

present day; yet we see none of the last of these classes and

hardly any traces of the two first at that period of the earth.

Where the iguanodon lived the elephant might have lived, but

there was no elephant at that time. The sea of the Lower Silurian

era was capable of supporting fish, but no fish existed. It

hence forcibly appears that theatres of life must have remained

unserviceable, or in the possession of a tenantry inferior to

what might have enjoyed them, for many ages: there surely would

have been no such waste allowed in a system where Omnipotence was

working upon the plan of minute attention to specialities. The

fact seems to denote that the actual procedure of the peopling of

the earth was one of a natural kind, requiring a long space of

time for its evolution. In this supposition the long existence

of land without land animals, and more particularly without the

noblest classes and orders, is only analogous to the fact, not

nearly enough present to the minds of a civilized people, that to

this day the bulk of the earth is a waste as far as man is


"Another startling objection is in the infinite local variation

of organic forms. Did the vegetable and animal kingdoms consist

of a definite number of species adapted to peculiarities of soil

and climate, and universally distributed, the fact would be in

harmony with the idea of special exertion. But the truth is that

various regions exhibit variations altogether without apparent

end or purpose. Professor Henslow enumerates forty-five distinct

flowers or sets of plants upon the surface of the earth,

notwithstanding that many of these would be equally suitable

elsewhere. The animals of different continents are equally

various, few species being the same in any two, though the

general character may conform. The inference at present drawn

from this fact is that there must have been, to use the language

of the Rev. Dr. Pye Smith, 'separate and original creations,

perhaps at different and respectively distinct epochs.' It seems

hardly conceivable that rational men should give an adherence to

such a doctrine when we think of what it involves. In the single

fact that it necessitates a special fiat of the inconceivable

Author of this sand-cloud of worlds to produce the flora of St.

Helena, we read its more than sufficient condemnation. It surely

harmonizes far better with our general ideas of nature to suppose

that, just as all else in this far-spread science was formed on

the laws impressed upon it at first by its Author, so also was

this. An exception presented to us in such a light appears

admissible only when we succeed in forbidding our minds to follow

out those reasoning processes to which, by another law of the

Almighty, they tend, and for which they are adapted."[4]

Such reasoning as this naturally aroused bitter animadversions,

and cannot have been without effect in creating an undercurrent

of thought in opposition to the main trend of opinion of the

time. But the book can hardly be said to have done more than

that. Indeed, some critics have denied it even this merit. After

its publication, as before, the conception of transmutation of

species remained in the popular estimation, both lay and

scientific, an almost forgotten "heresy."

It is true that here and there a scientist of greater or less

repute--as Von Buch, Meckel, and Von Baer in Germany, Bory

Saint-Vincent in France, Wells, Grant, and Matthew in England,

and Leidy in America--had expressed more or less tentative

dissent from the doctrine of special creation and immutability of

species, but their unaggressive suggestions, usually put forward

in obscure publications, and incidentally, were utterly

overlooked and ignored. And so, despite the scientific advances

along many lines at the middle of the century, the idea of the

transmutability of organic races had no such prominence, either

in scientific or unscientific circles, as it had acquired fifty

years before. Special creation held the day, seemingly unopposed.


But even at this time the fancied security of the

special-creation hypothesis was by no means real. Though it

seemed so invincible, its real position was that of an apparently

impregnable fortress beneath which, all unbeknown to the

garrison, a powder-mine has been dug and lies ready for

explosion. For already there existed in the secluded work-room of

an English naturalist, a manuscript volume and a portfolio of

notes which might have sufficed, if given publicity, to shatter

the entire structure of the special-creation hypothesis. The

naturalist who, by dint of long and patient effort, had

constructed this powder-mine of facts was Charles Robert Darwin,

grandson of the author of Zoonomia.

As long ago as July 1, 1837, young Darwin, then twenty-eight

years of age, had opened a private journal, in which he purposed

to record all facts that came to him which seemed to have any

bearing on the moot point of the doctrine of transmutation of

species. Four or five years earlier, during the course of that

famous trip around the world with Admiral Fitzroy, as naturalist

to the Beagle, Darwin had made the personal observations which

first tended to shake his belief of the fixity of species. In

South America, in the Pampean formation, he had discovered "great

fossil animals covered with armor like that on the existing

armadillos," and had been struck with this similarity of type

between ancient and existing faunas of the same region. He was

also greatly impressed by the manner in which closely related

species of animals were observed to replace one another as he

proceeded southward over the continent; and "by the

South-American character of most of the productions of the

Galapagos Archipelago, and more especially by the manner in which

they differ slightly on each island of the group, none of the

islands appearing to be very ancient in a geological sense."

At first the full force of these observations did not strike him;

for, under sway of Lyell's geological conceptions, he tentatively

explained the relative absence of life on one of the Galapagos

Islands by suggesting that perhaps no species had been created

since that island arose. But gradually it dawned upon him that

such facts as he had observed "could only be explained on the

supposition that species gradually become modified." From then

on, as he afterwards asserted, the subject haunted him; hence the

journal of 1837.

It will thus be seen that the idea of the variability of species

came to Charles Darwin as an inference from personal observations

in the field, not as a thought borrowed from books. He had, of

course, read the works of his grandfather much earlier in life,

but the arguments of Zoonomia and The Temple of Nature had not

served in the least to weaken his acceptance of the current

belief in fixity of species. Nor had he been more impressed with

the doctrine of Lamarck, so closely similar to that of his

grandfather. Indeed, even after his South-American experience

had aroused him to a new point of view he was still unable to see

anything of value in these earlier attempts at an explanation of

the variation of species. In opening his journal, therefore, he

had no preconceived notion of upholding the views of these or any

other makers of hypotheses, nor at the time had he formulated any

hypothesis of his own. His mind was open and receptive; he was

eager only for facts which might lead him to an understanding of

a problem which seemed utterly obscure. It was something to feel

sure that species have varied; but how have such variations been

brought about?

It was not long before Darwin found a clew which he thought might

lead to the answer he sought. In casting about for facts he had

soon discovered that the most available field for observation lay

among domesticated animals, whose numerous variations within

specific lines are familiar to every one. Thus under

domestication creatures so tangibly different as a mastiff and a

terrier have sprung from a common stock. So have the Shetland

pony, the thoroughbred, and the draught-horse. In short, there is

no domesticated animal that has not developed varieties deviating

more or less widely from the parent stock. Now, how has this been

accomplished? Why, clearly, by the preservation, through

selective breeding, of seemingly accidental variations. Thus one

horseman, by constantly selecting animals that "chance" to have

the right build and stamina, finally develops a race of

running-horses; while another horseman, by selecting a different

series of progenitors, has developed a race of slow, heavy

draught animals.

So far, so good; the preservation of "accidental" variations

through selective breeding is plainly a means by which races may

be developed that are very different from their original parent

form. But this is under man's supervision and direction. By what

process could such selection be brought about among creatures in

a state of nature? Here surely was a puzzle, and one that must be

solved before another step could be taken in this direction.

The key to the solution of this puzzle came into Darwin's mind

through a chance reading of the famous essay on "Population"

which Thomas Robert Malthus had published almost half a century

before. This essay, expositing ideas by no means exclusively

original with Malthus, emphasizes the fact that organisms tend to

increase at a geometrical ratio through successive generations,

and hence would overpopulate the earth if not somehow kept in

check. Cogitating this thought, Darwin gained a new insight into

the processes of nature. He saw that in virtue of this tendency

of each race of beings to overpopulate the earth, the entire

organic world, animal and vegetable, must be in a state of

perpetual carnage and strife, individual against individual,

fighting for sustenance and life.

That idea fully imagined, it becomes plain that a selective

influence is all the time at work in nature, since only a few

individuals, relatively, of each generation can come to maturity,

and these few must, naturally, be those best fitted to battle

with the particular circumstances in the midst of which they are

placed. In other words, the individuals best adapted to their

surroundings will, on the average, be those that grow to maturity

and produce offspring. To these offspring will be transmitted the

favorable peculiarities. Thus these peculiarities will become

permanent, and nature will have accomplished precisely what the

human breeder is seen to accomplish. Grant that organisms in a

state of nature vary, however slightly, one from another (which

is indubitable), and that such variations will be transmitted by

a parent to its offspring (which no one then doubted); grant,

further, that there is incessant strife among the various

organisms, so that only a small proportion can come to

maturity--grant these things, said Darwin, and we have an

explanation of the preservation of variations which leads on to

the transmutation of species themselves.

This wonderful coign of vantage Darwin had reached by 1839. Here

was the full outline of his theory; here were the ideas which

afterwards came to be embalmed in familiar speech in the phrases

"spontaneous variation," and the "survival of the fittest,"

through "natural selection." After such a discovery any ordinary

man would at once have run through the streets of science, so to

speak, screaming "Eureka!" Not so Darwin. He placed the

manuscript outline of his theory in his portfolio, and went on

gathering facts bearing on his discovery. In 1844 he made an

abstract in a manuscript book of the mass of facts by that time

accumulated. He showed it to his friend Hooker, made careful

provision for its publication in the event of his sudden death,

then stored it away in his desk and went ahead with the gathering

of more data. This was the unexploded powder-mine to which I have

just referred.

Twelve years more elapsed--years during which the silent worker

gathered a prodigious mass of facts, answered a multitude of

objections that arose in his own mind, vastly fortified his

theory. All this time the toiler was an invalid, never knowing a

day free from illness and discomfort, obliged to husband his

strength, never able to work more than an hour and a half at a

stretch; yet he accomplished what would have been vast

achievements for half a dozen men of robust health. Two friends

among the eminent scientists of the day knew of his labors--Sir

Joseph Hooker, the botanist, and Sir Charles Lyell, the

geologist. Gradually Hooker had come to be more than half a

convert to Darwin's views. Lyell was still sceptical, yet he

urged Darwin to publish his theory without further delay lest he

be forestalled. At last the patient worker decided to comply with

this advice, and in 1856 he set to work to make another and

fuller abstract of the mass of data he had gathered.

And then a strange thing happened. After Darwin had been at work

on his "abstract" about two years, but before he had published a

line of it, there came to him one day a paper in manuscript, sent

for his approval by a naturalist friend named Alfred Russel

Wallace, who had been for some time at work in the East India

Archipelago. He read the paper, and, to his amazement, found

that it contained an outline of the same theory of "natural

selection" which he himself had originated and for twenty years

had worked upon. Working independently, on opposite sides of the

globe, Darwin and Wallace had hit upon the same explanation of

the cause of transmutation of species. "Were Wallace's paper an

abstract of my unpublished manuscript of 1844," said Darwin, "it

could not better express my ideas."

Here was a dilemma. To publish this paper with no word from

Darwin would give Wallace priority, and wrest from Darwin the

credit of a discovery which he had made years before his

codiscoverer entered the field. Yet, on the other hand, could

Darwin honorably do otherwise than publish his friend's paper and

himself remain silent? It was a complication well calculated to

try a man's soul. Darwin's was equal to the test. Keenly alive

to the delicacy of the position, he placed the whole matter

before his friends Hooker and Lyell, and left the decision as to

a course of action absolutely to them. Needless to say, these

great men did the one thing which insured full justice to all

concerned. They counselled a joint publication, to include on the

one hand Wallace's paper, and on the other an abstract of

Darwin's ideas, in the exact form in which it had been outlined

by the author in a letter to Asa Gray in the previous year--an

abstract which was in Gray's hands before Wallace's paper was in

existence. This joint production, together with a full statement

of the facts of the case, was presented to the Linnaean Society

of London by Hooker and Lyell on the evening of July 1, 1858,

this being, by an odd coincidence, the twenty-first anniversary

of the day on which Darwin had opened his journal to collect

facts bearing on the "species question." Not often before in the

history of science has it happened that a great theory has been

nurtured in its author's brain through infancy and adolescence to

its full legal majority before being sent out into the world.

Thus the fuse that led to the great powder-mine had been lighted.

The explosion itself came more than a year later, in November,

1859, when Darwin, after thirteen months of further effort,

completed the outline of his theory, which was at first begun as

an abstract for the Linnaean Society, but which grew to the size

of an independent volume despite his efforts at condensation, and

which was given that ever-to-be-famous title, The Origin of

Species by Means of Natural Selection, or the Preservation of

Favored Races in the Struggle for Life. And what an explosion it

was! The joint paper of 1858 had made a momentary flare, causing

the hearers, as Hooker said, to "speak of it with bated breath,"

but beyond that it made no sensation. What the result was when

the Origin itself appeared no one of our generation need be told.

The rumble and roar that it made in the intellectual world have

not yet altogether ceased to echo after more than forty years of



To the Origin of Species, then, and to its author, Charles

Darwin, must always be ascribed chief credit for that vast

revolution in the fundamental beliefs of our race which has come

about since 1859, and which made the second half of the century

memorable. But it must not be overlooked that no such sudden

metamorphosis could have been effected had it not been for the

aid of a few notable lieutenants, who rallied to the standards of

the leader immediately after the publication of the Origin.

Darwin had all along felt the utmost confidence in the ultimate

triumph of his ideas. "Our posterity," he declared, in a letter

to Hooker, "will marvel as much about the current belief [in

special creation] as we do about fossil shells having been

thought to be created as we now see them." But he fully realized

that for the present success of his theory of transmutation the

championship of a few leaders of science was all-essential. He

felt that if he could make converts of Hooker and Lyell and of

Thomas Henry Huxley at once, all would be well.

His success in this regard, as in others, exceeded his

expectations. Hooker was an ardent disciple from reading the

proof-sheets before the book was published; Lyell renounced his

former beliefs and fell into line a few months later; while

Huxley, so soon as he had mastered the central idea of natural

selection, marvelled that so simple yet all-potent a thought had

escaped him so long, and then rushed eagerly into the fray,

wielding the keenest dialectic blade that was drawn during the

entire controversy. Then, too, unexpected recruits were found in

Sir John Lubbock and John Tyndall, who carried the war eagerly

into their respective territories; while Herbert Spencer, who had

advocated a doctrine of transmutation on philosophic grounds some

years before Darwin published the key to the mystery--and who

himself had barely escaped independent discovery of that

key--lent his masterful influence to the cause. In America the

famous botanist Asa Gray, who had long been a correspondent of

Darwin's but whose advocacy of the new theory had not been

anticipated, became an ardent propagandist; while in Germany

Ernst Heinrich Haeckel, the youthful but already noted zoologist,

took up the fight with equal enthusiasm.

Against these few doughty champions--with here and there another

of less general renown--was arrayed, at the outset, practically

all Christendom. The interest of the question came home to every

person of intelligence, whatever his calling, and the more deeply

as it became more and more clear how far-reaching are the real

bearings of the doctrine of natural selection. Soon it was seen

that should the doctrine of the survival of the favored races

through the struggle for existence win, there must come with it

as radical a change in man's estimate of his own position as had

come in the day when, through the efforts of Copernicus and

Galileo, the world was dethroned from its supposed central

position in the universe. The whole conservative majority of

mankind recoiled from this necessity with horror. And this

conservative majority included not laymen merely, but a vast

preponderance of the leaders of science also.

With the open-minded minority, on the other hand, the theory of

natural selection made its way by leaps and bounds. Its

delightful simplicity--which at first sight made it seem neither

new nor important--coupled with the marvellous comprehensiveness

of its implications, gave it a hold on the imagination, and

secured it a hearing where other theories of transmutation of

species had been utterly scorned. Men who had found Lamarck's

conception of change through voluntary effort ridiculous, and the

vaporings of the Vestiges altogether despicable, men whose

scientific cautions held them back from Spencer's deductive

argument, took eager hold of that tangible, ever-present

principle of natural selection, and were led on and on to its

goal. Hour by hour the attitude of the thinking world towards

this new principle changed; never before was so great a

revolution wrought so suddenly.

Nor was this merely because "the times were ripe" or "men's minds

prepared for evolution." Darwin himself bears witness that this

was not altogether so. All through the years in which he brooded

this theory he sounded his scientific friends, and could find

among them not one who acknowledged a doctrine of transmutation.

The reaction from the stand-point of Lamarck and Erasmus Darwin

and Goethe had been complete, and when Charles Darwin avowed his

own conviction he expected always to have it met with ridicule or

contempt. In 1857 there was but one man speaking with any large

degree of authority in the world who openly avowed a belief in

transmutation of species--that man being Herbert Spencer. But

the Origin of Species came, as Huxley has said, like a flash in

the darkness, enabling the benighted voyager to see the way. The

score of years during which its author had waited and worked had

been years well spent. Darwin had become, as he himself says, a

veritable Croesus, "overwhelmed with his riches in facts"--facts

of zoology, of selective artificial breeding, of geographical

distribution of animals, of embryology, of paleontology. He had

massed his facts about his theory, condensed them and

recondensed, until his volume of five hundred pages was an

encyclopaedia in scope. During those long years of musing he had

thought out almost every conceivable objection to his theory, and

in his book every such objection was stated with fullest force

and candor, together with such reply as the facts at command

might dictate. It was the force of those twenty years of effort

of a master-mind that made the sudden breach in the

breaswtork{sic} of current thought.

Once this breach was effected the work of conquest went rapidly

on. Day by day squads of the enemy capitulated and struck their

arms. By the time another score of years had passed the doctrine

of evolution had become the working hypothesis of the scientific

world. The revolution had been effected.

And from amid the wreckage of opinion and belief stands forth the

figure of Charles Darwin, calm, imperturbable, serene; scatheless

to ridicule, contumely, abuse; unspoiled by ultimate success;

unsullied alike by the strife and the victory--take him for all

in all, for character, for intellect, for what he was and what he

did, perhaps the most Socratic figure of the century. When, in

1882, he died, friend and foe alike conceded that one of the

greatest sons of men had rested from his labors, and all the

world felt it fitting that the remains of Charles Darwin should

be entombed in Westminster Abbey close beside the honored grave

of Isaac Newton. Nor were there many who would dispute the

justice of Huxley's estimate of his accomplishment: "He found a

great truth trodden under foot. Reviled by bigots, and ridiculed

by all the world, he lived long enough to see it, chiefly by his

own efforts, irrefragably established in science, inseparably

incorporated with the common thoughts of men, and only hated and

feared by those who would revile but dare not."


Wide as are the implications of the great truth which Darwin and

his co-workers established, however, it leaves quite untouched

the problem of the origin of those "favored variations" upon

which it operates. That such variations are due to fixed and

determinate causes no one understood better than Darwin; but in

his original exposition of his doctrine he made no assumption as

to what these causes are. He accepted the observed fact of

variation--as constantly witnessed, for example, in the

differences between parents and offspring--and went ahead from

this assumption.

But as soon as the validity of the principle of natural selection

came to be acknowledged speculators began to search for the

explanation of those variations which, for purposes of argument,

had been provisionally called "spontaneous." Herbert Spencer had

all along dwelt on this phase of the subject, expounding the

Lamarckian conceptions of the direct influence of the environment

(an idea which had especially appealed to Buffon and to Geoffroy

Saint-Hilaire), and of effort in response to environment and

stimulus as modifying the individual organism, and thus supplying

the basis for the operation of natural selection. Haeckel also

became an advocate of this idea, and presently there arose a

so-called school of neo-Lamarckians, which developed particular

strength and prominence in America under the leadership of

Professors A. Hyatt and E. D. Cope.

But just as the tide of opinion was turning strongly in this

direction, an utterly unexpected obstacle appeared in the form of

the theory of Professor August Weismann, put forward in 1883,

which antagonized the Lamarckian conception (though not touching

the Darwinian, of which Weismann is a firm upholder) by denying

that individual variations, however acquired by the mature

organism, are transmissible. The flurry which this denial created

has not yet altogether subsided, but subsequent observations seem

to show that it was quite disproportionate to the real merits of

the case. Notwithstanding Professor Weismann's objections, the

balance of evidence appears to favor the view that the Lamarckian

factor of acquired variations stands as the complement of the

Darwinian factor of natural selection in effecting the

transmutation of species.

Even though this partial explanation of what Professor Cope calls

the "origin of the fittest" be accepted, there still remains one

great life problem which the doctrine of evolution does not

touch. The origin of species, genera, orders, and classes of

beings through endless transmutations is in a sense explained;

but what of the first term of this long series? Whence came that

primordial organism whose transmuted descendants make up the

existing faunas and floras of the globe?

There was a time, soon after the doctrine of evolution gained a

hearing, when the answer to that question seemed to some

scientists of authority to have been given by experiment.

Recurring to a former belief, and repeating some earlier

experiments, the director of the Museum of Natural History at

Rouen, M. F. A. Pouchet, reached the conclusion that organic

beings are spontaneously generated about us constantly, in the

familiar processes of putrefaction, which were known to be due to

the agency of microscopic bacteria. But in 1862 Louis Pasteur

proved that this seeming spontaneous generation is in reality due

to the existence of germs in the air. Notwithstanding the

conclusiveness of these experiments, the claims of Pouchet were

revived in England ten years later by Professor Bastian; but then

the experiments of John Tyndall, fully corroborating the results

of Pasteur, gave a final quietus to the claim of "spontaneous

generation" as hitherto formulated.

There for the moment the matter rests. But the end is not yet.

Fauna and flora are here, and, thanks to Lamarck and Wallace and

Darwin, their development, through the operation of those

"secondary causes" which we call laws of nature, has been

proximally explained. The lowest forms of life have been linked

with the highest in unbroken chains of descent. Meantime,

through the efforts of chemists and biologists, the gap between

the inorganic and the organic worlds, which once seemed almost

infinite, has been constantly narrowed. Already philosophy can

throw a bridge across that gap. But inductive science, which

builds its own bridges, has not yet spanned the chasm, small

though it appear. Until it shall have done so, the bridge of

organic evolution is not quite complete; yet even as it stands

to-day it is perhaps the most stupendous scientific structure of

the nineteenth century.



At least two pupils of William Harvey distinguished themselves in

medicine, Giorgio Baglivi (1669-1707), who has been called the

"Italian Sydenham," and Hermann Boerhaave (1668-1738). The work

of Baglivi was hardly begun before his early death removed one of

the most promising of the early eighteenth-century physicians.

Like Boerhaave, he represents a type of skilled, practical

clinitian rather than the abstract scientist. One of his

contributions to medical literature is the first accurate

description of typhoid, or, as he calls it, mesenteric fever.

If for nothing else, Boerhaave must always be remembered as the

teacher of Von Haller, but in his own day he was the widest known

and the most popular teacher in the medical world. He was the

idol of his pupils at Leyden, who flocked to his lectures in such

numbers that it became necessary to "tear down the walls of

Leyden to accommodate them." His fame extended not only all over

Europe but to Asia, North America, and even into South America.

A letter sent him from China was addressed to "Boerhaave in

Europe." His teachings represent the best medical knowledge of

his day, a high standard of morality, and a keen appreciation of

the value of observation; and it was through such teachings

imparted to his pupils and advanced by them, rather than to any

new discoveries, that his name is important in medical history.

His arrangement and classification of the different branches of

medicine are interesting as representing the attitude of the

medical profession towards these various branches at that time.

"In the first place we consider Life; then Health, afterwards

Diseases; and lastly their several Remedies.

"Health the first general branch of Physic in our Institutions is

termed Physiology, or the Animal Oeconomy; demonstrating the

several Parts of the human Body, with their Mechanism and


"The second branch of Physic is called Pathology, treating of

Diseases, their Differences, Causes and Effects, or Symptoms; by

which the human Body is known to vary from its healthy state.

"The third part of Physic is termed Semiotica, which shows the

Signs distinguishing between sickness and Health, Diseases and

their Causes in the human Body; it also imports the State and

Degrees of Health and Diseases, and presages their future Events.

"The fourth general branch of Physic is termed Hygiene, or


"The fifth and last part of Physic is called Therapeutica; which

instructs us in the Nature, Preparation and uses of the Materia

Medica; and the methods of applying the same, in order to cure

Diseases and restore lost Health."[1]

From this we may gather that his general view of medicine was not

unlike that taken at the present time.

Boerhaave's doctrines were arranged into a "system" by Friedrich

Hoffmann, of Halle (1660-1742), this system having the merit of

being simple and more easily comprehended than many others. In

this system forces were considered inherent in matter, being

expressed as mechanical movements, and determined by mass,

number, and weight. Similarly, forces express themselves in the

body by movement, contraction, and relaxation, etc., and life

itself is movement, "particularly movement of the heart." Life

and death are, therefore, mechanical phenomena, health is

determined by regularly recurring movements, and disease by

irregularity of them. The body is simply a large hydraulic

machine, controlled by "the aether" or "sensitive soul," and the

chief centre of this soul lies in the medulla.

In the practical application of medicines to diseases Hoffman

used simple remedies, frequently with happy results, for whatever

the medical man's theory may be he seldom has the temerity to

follow it out logically, and use the remedies indicated by his

theory to the exclusion of long-established, although perhaps

purely empirical, remedies. Consequently, many vague theorists

have been excellent practitioners, and Hoffman was one of these.

Some of the remedies he introduced are still in use, notably the

spirits of ether, or "Hoffman's anodyne."


Besides Hoffman's system of medicine, there were numerous others

during the eighteenth century, most of which are of no importance

whatever; but three, at least, that came into existence and

disappeared during the century are worthy of fuller notice. One

of these, the Animists, had for its chief exponent Georg Ernst

Stahl of "phlogiston" fame; another, the Vitalists, was

championed by Paul Joseph Barthez (1734-1806); and the third was

the Organicists. This last, while agreeing with the other two

that vital activity cannot be explained by the laws of physics

and chemistry, differed in not believing that life "was due to

some spiritual entity," but rather to the structure of the body


The Animists taught that the soul performed functions of ordinary

life in man, while the life of lower animals was controlled by

ordinary mechanical principles. Stahl supported this theory

ardently, sometimes violently, at times declaring that there were

"no longer any doctors, only mechanics and chemists." He denied

that chemistry had anything to do with medicine, and, in the

main, discarded anatomy as useless to the medical man. The soul,

he thought, was the source of all vital movement; and the

immediate cause of death was not disease but the direct action of

the soul. When through some lesion, or because the machinery of

the body has become unworkable, as in old age, the soul leaves

the body and death is produced. The soul ordinarily selects the

channels of the circulation, and the contractile parts, as the

route for influencing the body. Hence in fever the pulse is

quickened, due to the increased activity of the soul, and

convulsions and spasmodic movements in disease are due, to the,

same cause. Stagnation of the, blood was supposed to be a

fertile cause of diseases, and such diseases were supposed to

arise mostly from "plethora"--an all-important element in Stahl's

therapeutics. By many this theory is regarded as an attempt on

the part of the pious Stahl to reconcile medicine and theology in

a way satisfactory to both physicians and theologians, but, like

many conciliatory attempts, it was violently opposed by both

doctors and ministers.

A belief in such a theory would lead naturally to simplicity in

therapeutics, and in this respect at least Stahl was consistent.

Since the soul knew more about the body than any physician could

know, Stahl conceived that it would be a hinderance rather than a

help for the physician to interfere with complicated doses of

medicine. As he advanced in age this view of the administration

of drugs grew upon him, until after rejecting quinine, and

finally opium, he at last used only salt and water in treating

his patients. From this last we may judge that his "system," if

not doing much good, was at least doing little harm.

The theory of the Vitalists was closely allied to that of the

Animists, and its most important representative, Paul Joseph

Barthez, was a cultured and eager scientist. After an eventful

and varied career as physician, soldier, editor, lawyer, and

philosopher in turn, he finally returned to the field of

medicine, was made consulting physician by Napoleon in 1802, and

died in Paris four years later.

The theory that he championed was based on the assumption that

there was a "vital principle," the nature of which was unknown,

but which differed from the thinking mind, and was the cause of

the phenomena of life. This "vital principle" differed from the

soul, and was not exhibited in human beings alone, but even in

animals and plants. This force, or whatever it might be called,

was supposed to be present everywhere in the body, and all

diseases were the results of it.

The theory of the Organicists, like that of the Animists and

Vitalists, agreed with the other two that vital activity could

not be explained by the laws of physics and chemistry, but,

unlike them, it held that it was a part of the structure of the

body itself. Naturally the practical physicians were more

attracted by this tangible doctrine than by vague theories "which

converted diseases into unknown derangements of some equally

unknown 'principle.' "

It is perhaps straining a point to include this brief description

of these three schools of medicine in the history of the progress

of the science. But, on the whole, they were negatively at least

prominent factors in directing true progress along its proper

channel, showing what courses were not to be pursued. Some one

has said that science usually stumbles into the right course only

after stumbling into all the wrong ones; and if this be only

partially true, the wrong ones still play a prominent if not a

very creditable part. Thus the medical systems of William Cullen

(1710-1790), and John Brown (1735-1788), while doing little

towards the actual advancement of scientific medicine, played so

conspicuous a part in so wide a field that the "Brunonian system"

at least must be given some little attention.

According to Brown's theory, life, diseases, and methods of cure

are explained by the property of "excitability." All exciting

powers were supposed to be stimulating, the apparent debilitating

effects of some being due to a deficiency in the amount of

stimulus. Thus "the whole phenomena of life, health, as well as

disease, were supposed to consist of stimulus and nothing else."

This theory created a great stir in the medical world, and

partisans and opponents sprang up everywhere. In Italy it was

enthusiastically supported; in England it was strongly opposed;

while in Scotland riots took place between the opposing factions.

Just why this system should have created any stir, either for or

against it, is not now apparent.

Like so many of the other "theorists" of his century, Brown's

practical conclusions deduced from his theory (or perhaps in

spite of it) were generally beneficial to medicine, and some of

them extremely valuable in the treatment of diseases. He first

advocated the modern stimulant, or "feeding treatment" of fevers,

and first recognized the usefulness of animal soups and beef-tea

in certain diseases.


Just at the close of the century there came into prominence the

school of homoeopathy, which was destined to influence the

practice of medicine very materially and to outlive all the other

eighteenth-century schools. It was founded by Christian Samuel

Friedrich Hahnemann (1755-1843), a most remarkable man, who,

after propounding a theory in his younger days which was at least

as reasonable as most of the existing theories, had the

misfortune to outlive his usefulness and lay his doctrine open to

ridicule by the unreasonable teachings of his dotage,

Hahnemann rejected all the teachings of morbid anatomy and

pathology as useless in practice, and propounded his famous

"similia similibus curantur"--that all diseases were to be cured

by medicine which in health produced symptoms dynamically similar

to the disease under treatment. If a certain medicine produced a

headache when given to a healthy person, then this medicine was

indicated in case of headaches, etc. At the present time such a

theory seems crude enough, but in the latter part of the

eighteenth century almost any theory was as good as the ones

propounded by Animists, Vitalists, and other such schools. It

certainly had the very commendable feature of introducing

simplicity in the use of drugs in place of the complicated

prescriptions then in vogue. Had Hahnemann stopped at this point

he could not have been held up to the indefensible ridicule that

was brought upon him, with considerable justice, by his later

theories. But he lived onto propound his extraordinary theory of

"potentiality"--that medicines gained strength by being

diluted--and his even more extraordinary theory that all chronic

diseases are caused either by the itch, syphilis, or fig-wart

disease, or are brought on by medicines.

At the time that his theory of potentialities was promulgated,

the medical world had gone mad in its administration of huge

doses of compound mixtures of drugs, and any reaction against

this was surely an improvement. In short, no medicine at all was

much better than the heaping doses used in common practice; and

hence one advantage, at least, of Hahnemann's methods. Stated

briefly, his theory was that if a tincture be reduced to

one-fiftieth in strength, and this again reduced to one-fiftieth,

and this process repeated up to thirty such dilutions, the

potency of such a medicine will be increased by each dilution,

Hahnemann himself preferring the weakest, or, as he would call

it, the strongest dilution. The absurdity of such a theory is

apparent when it is understood that long before any drug has been

raised to its thirtieth dilution it has been so reduced in

quantity that it cannot be weighed, measured, or recognized as

being present in the solution at all by any means known to

chemists. It is but just to modern followers of homoeopathy to

say that while most of them advocate small dosage, they do not

necessarily follow the teachings of Hahnemann in this respect,

believing that the theory of the dose "has nothing more to do

with the original law of cure than the psora (itch) theory has;

and that it was one of the later creations of Hahnemann's mind."

Hahnemann's theory that all chronic diseases are derived from

either itch, syphilis, or fig-wart disease is no longer advocated

by his followers, because it is so easily disproved, particularly

in the case of itch. Hahnemann taught that fully three-quarters

of all diseases were caused by "itch struck in," and yet it had

been demonstrated long before his day, and can be demonstrated

any time, that itch is simply a local skin disease caused by a

small parasite.


All advances in science have a bearing, near or remote, on the

welfare of our race; but it remains to credit to the closing

decade of the eighteenth century a discovery which, in its power

of direct and immediate benefit to humanity, surpasses any other

discovery of this or any previous epoch. Needless to say, I refer

to Jenner's discovery of the method of preventing smallpox by

inoculation with the virus of cow-pox. It detracts nothing from

the merit of this discovery to say that the preventive power of

accidental inoculation had long been rumored among the peasantry

of England. Such vague, unavailing half-knowledge is often the

forerunner of fruitful discovery.

To all intents and purposes Jenner's discovery was original and

unique. Nor, considered as a perfect method, was it in any sense

an accident. It was a triumph of experimental science. The

discoverer was no novice in scientific investigation, but a

trained observer, who had served a long apprenticeship in

scientific observation under no less a scientist than the

celebrated John Hunter. At the age of twenty-one Jenner had gone

to London to pursue his medical studies, and soon after he proved

himself so worthy a pupil that for two years he remained a member

of Hunter's household as his favorite pupil. His taste for

science and natural history soon attracted the attention of Sir

Joseph Banks, who intrusted him with the preparation of the

zoological specimens brought back by Captain Cook's expedition in

1771. He performed this task so well that he was offered the

position of naturalist to the second expedition, but declined it,

preferring to take up the practice of his profession in his

native town of Berkeley.

His many accomplishments and genial personality soon made him a

favorite both as a physician and in society. He was a good

singer, a fair violinist and flute-player, and a very successful

writer of prose and verse. But with all his professional and

social duties he still kept up his scientific investigations,

among other things making some careful observations on the

hibernation of hedgehogs at the instigation of Hunter, the

results of which were laid before the Royal Society. He also

made quite extensive investigations as to the geological

formations and fossils found in his neighborhood.

Even during his student days with Hunter he had been much

interested in the belief, current in the rural districts of

Gloucestershire, of the antagonism between cow-pox and small-pox,

a person having suffered from cow-pox being immuned to small-pox.

At various times Jenner had mentioned the subject to Hunter, and

he was constantly making inquiries of his fellow-practitioners as

to their observations and opinions on the subject. Hunter was too

fully engrossed in other pursuits to give the matter much serious

attention, however, and Jenner's brothers of the profession gave

scant credence to the rumors, although such rumors were common


At this time the practice of inoculation for preventing

small-pox, or rather averting the severer forms of the disease,

was widely practised. It was customary, when there was a mild

case of the disease, to take some of the virus from the patient

and inoculate persons who had never had the disease, producing a

similar attack in them. Unfortunately there were many objections

to this practice. The inoculated patient frequently developed a

virulent form of the disease and died; or if he recovered, even

after a mild attack, he was likely to be "pitted" and disfigured.

But, perhaps worst of all, a patient so inoculated became the

source of infection to others, and it sometimes happened that

disastrous epidemics were thus brought about. The case was a

most perplexing one, for the awful scourge of small-pox hung

perpetually over the head of every person who had not already

suffered and recovered from it. The practice of inoculation was

introduced into England by Lady Mary Wortley Montague

(1690-1762), who had seen it practised in the East, and who

announced her intention of "introducing it into England in spite

of the doctors."

From the fact that certain persons, usually milkmaids, who had

suffered from cow-pox seemed to be immuned to small-pox, it would

seem a very simple process of deduction to discover that cow-pox

inoculation was the solution of the problem of preventing the

disease. But there was another form of disease which, while

closely resembling cow-pox and quite generally confounded with

it, did not produce immunity. The confusion of these two forms of

the disease had constantly misled investigations as to the

possibility of either of them immunizing against smallpox, and

the confusion of these two diseases for a time led Jenner to

question the possibility of doing so. After careful

investigations, however, he reached the conclusion that there was

a difference in the effects of the two diseases, only one of

which produced immunity from small-pox.

"There is a disease to which the horse, from his state of

domestication, is frequently subject," wrote Jenner, in his

famous paper on vaccination. "The farriers call it the grease.

It is an inflammation and swelling in the heel, accompanied at

its commencement with small cracks or fissures, from which issues

a limpid fluid possessing properties of a very peculiar kind.

This fluid seems capable of generating a disease in the human

body (after it has undergone the modification I shall presently

speak of) which bears so strong a resemblance to small-pox that I

think it highly probable it may be the source of that disease.

"In this dairy country a great number of cows are kept, and the

office of milking is performed indiscriminately by men and maid

servants. One of the former having been appointed to apply

dressings to the heels of a horse affected with the malady I have

mentioned, and not paying due attention to cleanliness,

incautiously bears his part in milking the cows with some

particles of the infectious matter adhering to his fingers. When

this is the case it frequently happens that a disease is

communicated to the cows, and from the cows to the dairy-maids,

which spreads through the farm until most of the cattle and

domestics feel its unpleasant consequences. This disease has

obtained the name of Cow-Pox. It appears on the nipples of the

cows in the form of irregular pustules. At their first appearance

they are commonly of a palish blue, or rather of a color somewhat

approaching to livid, and are surrounded by an inflammation.

These pustules, unless a timely remedy be applied, frequently

degenerate into phagedenic ulcers, which prove extremely

troublesome. The animals become indisposed, and the secretion of

milk is much lessened. Inflamed spots now begin to appear on

different parts of the hands of the domestics employed in

milking, and sometimes on the wrists, which run on to

suppuration, first assuming the appearance of the small

vesications produced by a burn. Most commonly they appear about

the joints of the fingers and at their extremities; but whatever

parts are affected, if the situation will admit the superficial

suppurations put on a circular form with their edges more

elevated than their centre and of a color distinctly approaching

to blue. Absorption takes place, and tumors appear in each

axilla. The system becomes affected, the pulse is quickened;

shiverings, succeeded by heat, general lassitude, and pains about

the loins and limbs, with vomiting, come on. The head is

painful, and the patient is now and then even affected with

delirium. These symptoms, varying in their degrees of violence,

generally continue from one day to three or four, leaving

ulcerated sores about the hands which, from the sensibility of

the parts, are very troublesome and commonly heal slowly,

frequently becoming phagedenic, like those from which they

sprang. During the progress of the disease the lips, nostrils,

eyelids, and other parts of the body are sometimes affected with

sores; but these evidently arise from their being heedlessly

rubbed or scratched by the patient's infected fingers. No

eruptions on the skin have followed the decline of the feverish

symptoms in any instance that has come under my inspection, one

only excepted, and in this case a very few appeared on the arms:

they were very minute, of a vivid red color, and soon died away

without advancing to maturation, so that I cannot determine

whether they had any connection with the preceding symptoms.

"Thus the disease makes its progress from the horse (as I

conceive) to the nipple of the cow, and from the cow to the human


"Morbid matter of various kinds, when absorbed into the system,

may produce effects in some degree similar; but what renders the

cow-pox virus so extremely singular is that the person that has

been thus affected is forever after secure from the infection of

small-pox, neither exposure to the variolous effluvia nor the

insertion of the matter into the skin producing this


In 1796 Jenner made his first inoculation with cowpox matter, and

two months later the same subject was inoculated with small-pox

matter. But, as Jenner had predicted, no attack of small-pox

followed. Although fully convinced by this experiment that the

case was conclusively proven, he continued his investigations,

waiting two years before publishing his discovery. Then,

fortified by indisputable proofs, he gave it to the world. The

immediate effects of his announcement have probably never been

equalled in the history of scientific discovery, unless, perhaps,

in the single instance of the discovery of anaesthesia. In Geneva

and Holland clergymen advocated the practice of vaccination from

their pulpits; in some of the Latin countries religious

processions were formed for receiving vaccination; Jenner's

birthday was celebrated as a feast in Germany; and the first

child vaccinated in Russia was named "Vaccinov" and educated at

public expense. In six years the discovery had penetrated to the

most remote corners of civilization; it had even reached some

savage nations. And in a few years small-pox had fallen from the

position of the most dreaded of all diseases to that of being

practically the only disease for which a sure and easy preventive

was known.

Honors were showered upon Jenner from the Old and the New World,

and even Napoleon, the bitter hater of the English, was among the

others who honored his name. On one occasion Jenner applied to

the Emperor for the release of certain Englishmen detained in

France. The petition was about to be rejected when the name of

the petitioner was mentioned. "Ah," said Napoleon, "we can refuse

nothing to that name!"

It is difficult for us of to-day clearly to conceive the

greatness of Jenner's triumph, for we can only vaguely realize

what a ruthless and ever-present scourge smallpox had been to all

previous generations of men since history began. Despite all

efforts to check it by medication and by direct inoculation, it

swept now and then over the earth as an all-devastating

pestilence, and year by year it claimed one-tenth of all the

beings in Christendom by death as its average quota of victims.

"From small-pox and love but few remain free," ran the old saw. A

pitted face was almost as much a matter of course a hundred years

ago as a smooth one is to-day.

Little wonder, then, that the world gave eager acceptance to

Jenner's discovery. No urging was needed to induce the majority

to give it trial; passengers on a burning ship do not hold aloof

from the life-boats. Rich and poor, high and low, sought succor

in vaccination and blessed the name of their deliverer. Of all

the great names that were before the world in the closing days of

the century, there was perhaps no other one at once so widely

known and so uniformly reverenced as that of the great English

physician Edward Jenner. Surely there was no other one that

should be recalled with greater gratitude by posterity.



Although Napoleon Bonaparte, First Consul, was not lacking in

self-appreciation, he probably did not realize that in selecting

a physician for his own needs he was markedly influencing the

progress of medical science as a whole. Yet so strangely are

cause and effect adjusted in human affairs that this simple act

of the First Consul had that very unexpected effect. For the man

chosen was the envoy of a new method in medical practice, and the

fame which came to him through being physician to the First

Consul, and subsequently to the Emperor, enabled him to

promulgate the method in a way otherwise impracticable. Hence the

indirect but telling value to medical science of Napoleon's


The physician in question was Jean Nicolas de Corvisart. His

novel method was nothing more startling than the now-familiar

procedure of tapping the chest of a patient to elicit sounds

indicative of diseased tissues within. Every one has seen this

done commonly enough in our day, but at the beginning of the

century Corvisart, and perhaps some of his pupils, were probably

the only physicians in the world who resorted to this simple and

useful procedure. Hence Napoleon's surprise when, on calling in

Corvisart, after becoming somewhat dissatisfied with his other

physicians Pinel and Portal, his physical condition was

interrogated in this strange manner. With characteristic

shrewdness Bonaparte saw the utility of the method, and the

physician who thus attempted to substitute scientific method for

guess-work in the diagnosis of disease at once found favor in his

eyes and was installed as his regular medical adviser.

For fifteen years before this Corvisart had practised percussion,

as the chest-tapping method is called, without succeeding in

convincing the profession of its value. The method itself, it

should be added, had not originated with Corvisart, nor did the

French physician for a moment claim it as his own. The true

originator of the practice was the German physician Avenbrugger,

who published a book about it as early as 1761. This book had

even been translated into French, then the language of

international communication everywhere, by Roziere de la

Chassagne, of Montpellier, in 1770; but no one other than

Corvisart appears to have paid any attention to either original

or translation. It was far otherwise, however, when Corvisart

translated Avenbrugger's work anew, with important additions of

his own, in 1808.

"I know very well how little reputation is allotted to translator

and commentators," writes Corvisart, "and I might easily have

elevated myself to the rank of an author if I had elaborated anew

the doctrine of Avenbrugger and published an independent work on

percussion. In this way, however, I should have sacrificed the

name of Avenbrugger to my own vanity, a thing which I am

unwilling to do. It is he, and the beautiful invention which of

right belongs to him, that I desire to recall to life."[1]

By this time a reaction had set in against the metaphysical

methods in medicine that had previously been so alluring; the

scientific spirit of the time was making itself felt in medical

practice; and this, combined with Corvisart's fame, brought the

method of percussion into immediate and well-deserved popularity.

Thus was laid the foundation for the method of so-called physical

diagnosis, which is one of the corner-stones of modern medicine.

The method of physical diagnosis as practised in our day was by

no means completed, however, with the work of Corvisart.

Percussion alone tells much less than half the story that may be

elicited from the organs of the chest by proper interrogation.

The remainder of the story can only be learned by applying the

ear itself to the chest, directly or indirectly. Simple as this

seems, no one thought of practising it for some years after

Corvisart had shown the value of percussion.

Then, in 1815, another Paris physician, Rene Theophile Hyacinthe

Laennec, discovered, almost by accident, that the sound of the

heart-beat could be heard surprisingly through a cylinder of

paper held to the ear and against the patient's chest. Acting on

the hint thus received, Laennec substituted a hollow cylinder of

wood for the paper, and found himself provided with an instrument

through which not merely heart sounds but murmurs of the lungs in

respiration could be heard with almost startling distinctness.

The possibility of associating the varying chest sounds with

diseased conditions of the organs within appealed to the fertile

mind of Laennec as opening new vistas in therapeutics, which he

determined to enter to the fullest extent practicable. His

connection with the hospitals of Paris gave him full opportunity

in this direction, and his labors of the next few years served

not merely to establish the value of the new method as an aid to

diagnosis, but laid the foundation also for the science of morbid

anatomy. In 1819 Laennec published the results of his labors in

a work called Traite d'Auscultation Mediate,[2] a work which

forms one of the landmarks of scientific medicine. By mediate

auscultation is meant, of course, the interrogation of the chest

with the aid of the little instrument already referred to, an

instrument which its originator thought hardly worth naming until

various barbarous appellations were applied to it by others,

after which Laennec decided to call it the stethoscope, a name

which it has ever since retained.

In subsequent years the form of the stethoscope, as usually

employed, was modified and its value augmented by a binauricular

attachment, and in very recent years a further improvement has

been made through application of the principle of the telephone;

but the essentials of auscultation with the stethoscope were

established in much detail by Laennec, and the honor must always

be his of thus taking one of the longest single steps by which

practical medicine has in our century acquired the right to be

considered a rational science. Laennec's efforts cost him his

life, for he died in 1826 of a lung disease acquired in the

course of his hospital practice; but even before this his fame

was universal, and the value of his method had been recognized

all over the world. Not long after, in 1828, yet another French

physician, Piorry, perfected the method of percussion by

introducing the custom of tapping, not the chest directly, but

the finger or a small metal or hard-rubber plate held against the

chest-mediate percussion, in short. This perfected the methods

of physical diagnosis of diseases of the chest in all essentials;

and from that day till this percussion and auscultation have held

an unquestioned place in the regular armamentarium of the


Coupled with the new method of physical diagnosis in the effort

to substitute knowledge for guess-work came the studies of the

experimental physiologists--in particular, Marshall Hall in

England and Francois Magendie in France; and the joint efforts of

these various workers led presently to the abandonment of those

severe and often irrational depletive methods--blood-letting and

the like--that had previously dominated medical practice. To this

end also the "statistical method," introduced by Louis and his

followers, largely contributed; and by the close of the first

third of our century the idea was gaining ground that the

province of therapeutics is to aid nature in combating disease,

and that this may often be accomplished better by simple means

than by the heroic measures hitherto thought necessary. In a

word, scientific empiricism was beginning to gain a hearing in

medicine as against the metaphysical preconceptions of the

earlier generations.


I have just adverted to the fact that Napoleon Bonaparte, as

First Consul and as Emperor, was the victim of a malady which

caused him to seek the advice of the most distinguished

physicians of Paris. It is a little shocking to modern

sensibilities to read that these physicians, except Corvisart,

diagnosed the distinguished patient's malady as "gale

repercutee"--that is to say, in idiomatic English, the itch

"struck in." It is hardly necessary to say that no physician of

today would make so inconsiderate a diagnosis in the case of a

royal patient. If by any chance a distinguished patient were

afflicted with the itch, the sagacious physician would carefully

hide the fact behind circumlocutions and proceed to eradicate the

disease with all despatch. That the physicians of Napoleon did

otherwise is evidence that at the beginning of the century the

disease in question enjoyed a very different status. At that

time itch, instead of being a most plebeian malady, was, so to

say, a court disease. It enjoyed a circulation, in high circles

and in low, that modern therapeutics has quite denied it; and the

physicians of the time gave it a fictitious added importance by

ascribing to its influence the existence of almost any obscure

malady that came under their observation. Long after Napoleon's

time gale continued to hold this proud distinction. For example,

the imaginative Dr. Hahnemann did not hesitate to affirm, as a

positive maxim, that three-fourths of all the ills that flesh is

heir to were in reality nothing but various forms of "gale


All of which goes to show how easy it may be for a masked

pretender to impose on credulous humanity, for nothing is more

clearly established in modern knowledge than the fact that "gale

repercutee" was simply a name to hide a profound ignorance; no

such disease exists or ever did exist. Gale itself is a

sufficiently tangible reality, to be sure, but it is a purely

local disease of the skin, due to a perfectly definite cause, and

the dire internal conditions formerly ascribed to it have really

no causal connection with it whatever. This definite cause, as

every one nowadays knows, is nothing more or less than a

microscopic insect which has found lodgment on the skin, and has

burrowed and made itself at home there. Kill that insect and the

disease is no more; hence it has come to be an axiom with the

modern physician that the itch is one of the three or four

diseases that he positively is able to cure, and that very

speedily. But it was far otherwise with the physicians of the

first third of our century, because to them the cause of the

disease was an absolute mystery.

It is true that here and there a physician had claimed to find an

insect lodged in the skin of a sufferer from itch, and two or

three times the claim had been made that this was the cause of

the malady, but such views were quite ignored by the general

profession, and in 1833 it was stated in an authoritative medical

treatise that the "cause of gale is absolutely unknown." But

even at this time, as it curiously happened, there were certain

ignorant laymen who had attained to a bit of medical knowledge

that was withheld from the inner circles of the profession. As

the peasantry of England before Jenner had known of the curative

value of cow-pox over small-pox, so the peasant women of Poland

had learned that the annoying skin disease from which they

suffered was caused by an almost invisible insect, and,

furthermore, had acquired the trick of dislodging the pestiferous

little creature with the point of a needle. From them a youth of

the country, F. Renucci by name, learned the open secret. He

conveyed it to Paris when he went there to study medicine, and in

1834 demonstrated it to his master Alibert. This physician, at

first sceptical, soon was convinced, and gave out the discovery

to the medical world with an authority that led to early


Now the importance of all this, in the present connection, is not

at all that it gave the clew to the method of cure of a single

disease. What makes the discovery epochal is the fact that it

dropped a brand-new idea into the medical ranks--an idea

destined, in the long-run, to prove itself a veritable bomb--the

idea, namely, that a minute and quite unsuspected animal parasite

may be the cause of a well-known, widely prevalent, and important

human disease. Of course the full force of this idea could only

be appreciated in the light of later knowledge; but even at the

time of its coming it sufficed to give a great impetus to that

new medical knowledge, based on microscopical studies, which had

but recently been made accessible by the inventions of the

lens-makers. The new knowledge clarified one very turbid medical

pool and pointed the way to the clarification of many others.

Almost at the same time that the Polish medical student was

demonstrating the itch mite in Paris, it chanced, curiously

enough, that another medical student, this time an Englishman,

made an analogous discovery of perhaps even greater importance.

Indeed, this English discovery in its initial stages slightly

antedated the other, for it was in 1833 that the student in

question, James Paget, interne in St. Bartholomew's Hospital,

London, while dissecting the muscular tissues of a human subject,

found little specks of extraneous matter, which, when taken to

the professor of comparative anatomy, Richard Owen, were

ascertained, with the aid of the microscope, to be the cocoon of

a minute and hitherto unknown insect. Owen named the insect

Trichina spiralis. After the discovery was published it

transpired that similar specks had been observed by several

earlier investigators, but no one had previously suspected or, at

any rate, demonstrated their nature. Nor was the full story of

the trichina made out for a long time after Owen's discovery. It

was not till 1847 that the American anatomist Dr. Joseph Leidy

found the cysts of trichina in the tissues of pork; and another

decade or so elapsed after that before German workers, chief

among whom were Leuckart, Virchow, and Zenker, proved that the

parasite gets into the human system through ingestion of infected

pork, and that it causes a definite set of symptoms of disease

which hitherto had been mistaken for rheumatism, typhoid fever,

and other maladies. Then the medical world was agog for a time

over the subject of trichinosis; government inspection of pork

was established in some parts of Germany; American pork was

excluded altogether from France; and the whole subject thus came

prominently to public attention. But important as the trichina

parasite proved on its own account in the end, its greatest

importance, after all, was in the share it played in directing

attention at the time of its discovery in 1833 to the subject of

microscopic parasites in general.

The decade that followed that discovery was a time of great

activity in the study of microscopic organisms and microscopic

tissues, and such men as Ehrenberg and Henle and Bory

Saint-Vincent and Kolliker and Rokitansky and Remak and Dujardin

were widening the bounds of knowledge of this new subject with

details that cannot be more than referred to here. But the

crowning achievement of the period in this direction was the

discovery made by the German, J. L. Schoenlein, in 1839, that a

very common and most distressing disease of the scalp, known as

favus, is really due to the presence and growth on the scalp of a

vegetable organism of microscopic size. Thus it was made clear

that not merely animal but also vegetable organisms of obscure,

microscopic species have causal relations to the diseases with

which mankind is afflicted. This knowledge of the parasites was

another long step in the direction of scientific medical

knowledge; but the heights to which this knowledge led were not

to be scaled, or even recognized, until another generation of

workers had entered the field.


Meantime, in quite another field of medicine, events were

developing which led presently to a revelation of greater

immediate importance to humanity than any other discovery that

had come in the century, perhaps in any field of science

whatever. This was the discovery of the pain-dispelling power of

the vapor of sulphuric ether inhaled by a patient undergoing a

surgical operation. This discovery came solely out of America,

and it stands curiously isolated, since apparently no minds in

any other country were trending towards it even vaguely. Davy,

in England, had indeed originated the method of medication by

inhalation, and earned out some most interesting experiments

fifty years earlier, and it was doubtless his experiments with

nitrous oxide gas that gave the clew to one of the American

investigators; but this was the sole contribution of preceding

generations to the subject, and since the beginning of the

century, when Davy turned his attention to other matters, no one

had made the slightest advance along the same line until an

American dentist renewed the investigation.

In view of the sequel, Davy's experiments merit full attention.

Here is his own account of them, as written in 1799:

"Immediately after a journey of one hundred and twenty-six miles,

in which I had no sleep the preceding night, being much

exhausted, I respired seven quarts of nitrous oxide gas for near

three minutes. It produced the usual pleasurable effects and

slight muscular motion. I continued exhilarated for some minutes

afterwards, but in half an hour found myself neither more nor

less exhausted than before the experiment. I had a great

propensity to sleep.

"To ascertain with certainty whether the more extensive action of

nitrous oxide compatible with life was capable of producing

debility, I resolved to breathe the gas for such a time, and in

such quantities, as to produce excitement equal in duration and

superior in intensity to that occasioned by high intoxication

from opium or alcohol.

"To habituate myself to the excitement, and to carry it on

gradually, on December 26th I was enclosed in an air-tight

breathing-box, of the capacity of about nine and one-half cubic

feet, in the presence of Dr. Kinglake. After I had taken a

situation in which I could by means of a curved thermometer

inserted under the arm, and a stop-watch, ascertain the

alterations in my pulse and animal heat, twenty quarts of nitrous

oxide were thrown into the box.

"For three minutes I experienced no alteration in my sensations,

though immediately after the introduction of the nitrous oxide

the smell and taste of it were very evident. In four minutes I

began to feel a slight glow in the cheeks and a generally

diffused warmth over the chest, though the temperature of the box

was not quite 50 degrees. . . . In twenty-five minutes the animal

heat was 100 degrees, pulse 124. In thirty minutes twenty quarts

more of gas were introduced.

"My sensations were now pleasant; I had a generally diffused

warmth without the slightest moisture of the skin, a sense of

exhilaration similar to that produced by a small dose of wine,

and a disposition to muscular motion and to merriment.

"In three-quarters of an hour the pulse was 104 and the animal

heat not 99.5 degrees, the temperature of the chamber 64 degrees.

The pleasurable feelings continued to increase, the pulse became

fuller and slower, till in about an hour it was 88, when the

animal heat was 99 degrees. Twenty quarts more of air were

admitted. I had now a great disposition to laugh, luminous points

seemed frequently to pass before my eyes, my hearing was

certainly more acute, and I felt a pleasant lightness and power

of exertion in my muscles. In a short time the symptoms became

stationary; breathing was rather oppressed, and on account of the

great desire for action rest was painful.

"I now came out of the box, having been in precisely an hour and

a quarter. The moment after I began to respire twenty quarts of

unmingled nitrous oxide. A thrilling extending from the chest to

the extremities was almost immediately produced. I felt a sense

of tangible extension highly pleasurable in every limb; my

visible impressions were dazzling and apparently magnified, I

heard distinctly every sound in the room, and was perfectly aware

of my situation. By degrees, as the pleasurable sensations

increased, I lost all connection with external things; trains of

vivid visible images rapidly passed through my mind and were

connected with words in such a manner as to produce perceptions

perfectly novel.

"I existed in a world of newly connected and newly modified

ideas. I theorized; I imagined that I made discoveries. When I

was awakened from this semi-delirious trance by Dr. Kinglake, who

took the bag from my mouth, indignation and pride were the first

feelings produced by the sight of persons about me. My emotions

were enthusiastic and sublime; and for a minute I walked about

the room perfectly regardless of what was said to me. As I

recovered my former state of mind, I felt an inclination to

communicate the discoveries I had made during the experiment. I

endeavored to recall the ideas--they were feeble and indistinct;

one collection of terms, however, presented itself, and, with

most intense belief and prophetic manner, I exclaimed to Dr.

Kinglake, 'Nothing exists but thoughts!--the universe is composed

of impressions, ideas, pleasures, and pains.' "[3]

From this account we see that Davy has anaesthetized himself to a

point where consciousness of surroundings was lost, but not past

the stage of exhilaration. Had Dr. Kinglake allowed the

inhaling-bag to remain in Davy's mouth for a few moments longer

complete insensibility would have followed. As it was, Davy

appears to have realized that sensibility was dulled, for he adds

this illuminative suggestion: "As nitrous oxide in its extensive

operation appears capable of destroying physical pain, it may

probably be used with advantage during surgical operations in

which no great effusion of blood takes place."[4]

Unfortunately no one took advantage of this suggestion at the

time, and Davy himself became interested in other fields of

science and never returned to his physiological studies, thus

barely missing one of the greatest discoveries in the entire

field of science. In the generation that followed no one seems to

have thought of putting Davy's suggestion to the test, and the

surgeons of Europe had acknowledged with one accord that all hope

of finding a means to render operations painless must be utterly

abandoned--that the surgeon's knife must ever remain a synonym

for slow and indescribable torture. By an odd coincidence it

chanced that Sir Benjamin Brodie, the acknowledged leader of

English surgeons, had publicly expressed this as his deliberate

though regretted opinion at a time when the quest which he

considered futile had already led to the most brilliant success

in America, and while the announcement of the discovery, which

then had no transatlantic cable to convey it, was actually on its

way to the Old World.

The American dentist just referred to, who was, with one

exception to be noted presently, the first man in the world to

conceive that the administration of a definite drug might render

a surgical operation painless and to give the belief application

was Dr. Horace Wells, of Hartford, Connecticut. The drug with

which he experimented was nitrous oxide--the same that Davy had

used; the operation that he rendered painless was no more

important than the extraction of a tooth--yet it sufficed to mark

a principle; the year of the experiment was 1844.

The experiments of Dr. Wells, however, though important, were not

sufficiently demonstrative to bring the matter prominently to the

attention of the medical world. The drug with which he

experimented proved not always reliable, and he himself seems

ultimately to have given the matter up, or at least to have

relaxed his efforts. But meantime a friend, to whom he had

communicated his belief and expectations, took the matter up, and

with unremitting zeal carried forward experiments that were

destined to lead to more tangible results. This friend was

another dentist, Dr. W. T. G. Morton, of Boston, then a young man

full of youthful energy and enthusiasm. He seems to have felt

that the drug with which Wells had experimented was not the most

practicable one for the purpose, and so for several months he

experimented with other allied drugs, until finally he hit upon

sulphuric ether, and with this was able to make experiments upon

animals, and then upon patients in the dental chair, that seemed

to him absolutely demonstrative.

Full of eager enthusiasm, and absolutely confident of his

results, he at once went to Dr. J. C. Warren, one of the foremost

surgeons of Boston, and asked permission to test his discovery

decisively on one of the patients at the Boston Hospital during a

severe operation. The request was granted; the test was made on

October 16, 1846, in the presence of several of the foremost

surgeons of the city and of a body of medical students. The

patient slept quietly while the surgeon's knife was plied, and

awoke to astonished comprehension that the ordeal was over. The

impossible, the miraculous, had been accomplished.[5]

Swiftly as steam could carry it--slowly enough we should think it

to-day--the news was heralded to all the world. It was received

in Europe with incredulity, which vanished before repeated

experiments. Surgeons were loath to believe that ether, a drug

that had long held a place in the subordinate armamentarium of

the physician, could accomplish such a miracle. But scepticism

vanished before the tests which any surgeon might make, and which

surgeons all over the world did make within the next few weeks.

Then there came a lingering outcry from a few surgeons, notably

some of the Parisians, that the shock of pain was beneficial to

the patient, hence that anaesthesia--as Dr. Oliver Wendell Holmes

had christened the new method--was a procedure not to be advised.

Then, too, there came a hue-and-cry from many a pulpit that pain

was God-given, and hence, on moral grounds, to be clung to rather

than renounced. But the outcry of the antediluvians of both

hospital and pulpit quickly received its quietus; for soon it was

clear that the patient who did not suffer the shock of pain

during an operation rallied better than the one who did so

suffer, while all humanity outside the pulpit cried shame to the

spirit that would doom mankind to suffer needless agony. And so

within a few months after that initial operation at the Boston

Hospital in 1846, ether had made good its conquest of pain

throughout the civilized world. Only by the most active use of

the imagination can we of this present day realize the full

meaning of that victory.

It remains to be added that in the subsequent bickerings over the

discovery--such bickerings as follow every great advance--two

other names came into prominent notice as sharers in the glory of

the new method. Both these were Americans--the one, Dr. Charles

T. Jackson, of Boston; the other, Dr. Crawford W. Long, of

Alabama. As to Dr. Jackson, it is sufficient to say that he

seems to have had some vague inkling of the peculiar properties

of ether before Morton's discovery. He even suggested the use of

this drug to Morton, not knowing that Morton had already tried

it; but this is the full measure of his association with the

discovery. Hence it is clear that Jackson's claim to equal share

with Morton in the discovery was unwarranted, not to say absurd.

Dr. Long's association with the matter was far different and

altogether honorable. By one of those coincidences so common in

the history of discovery, he was experimenting with ether as a

pain-destroyer simultaneously with Morton, though neither so much

as knew of the existence of the other. While a medical student he

had once inhaled ether for the intoxicant effects, as other

medical students were wont to do, and when partially under

influence of the drug he had noticed that a chance blow to his

shins was painless. This gave him the idea that ether might be

used in surgical operations; and in subsequent years, in the

course of his practice in a small Georgia town, he put the idea

into successful execution. There appears to be no doubt whatever

that he performed successful minor operations under ether some

two or three years before Morton's final demonstration; hence

that the merit of first using the drug, or indeed any drug, in

this way belongs to him. But, unfortunately, Dr. Long did not

quite trust the evidence of his own experiments. Just at that

time the medical journals were full of accounts of experiments in

which painless operations were said to be performed through

practice of hypnotism, and Dr. Long feared that his own success

might be due to an incidental hypnotic influence rather than to

the drug. Hence he delayed announcing his apparent discovery

until he should have opportunity for further tests--and

opportunities did not come every day to the country practitioner.

And while he waited, Morton anticipated him, and the discovery

was made known to the world without his aid. It was a true

scientific caution that actuated Dr. Long to this delay, but the

caution cost him the credit, which might otherwise have been his,

of giving to the world one of the greatest blessings--dare we

not, perhaps, say the very greatest?--that science has ever

conferred upon humanity.

A few months after the use of ether became general, the Scotch

surgeon Sir J. Y. Simpson[6] discovered that another drug,

chloroform, could be administered with similar effects; that it

would, indeed, in many cases produce anaesthesia more

advantageously even than ether. From that day till this surgeons

have been more or less divided in opinion as to the relative

merits of the two drugs; but this fact, of course, has no bearing

whatever upon the merit of the first discovery of the method of

anaesthesia. Even had some other drug subsequently quite

banished ether, the honor of the discovery of the beneficent

method of anaesthesia would have been in no wise invalidated. And

despite all cavillings, it is unequivocally established that the

man who gave that method to the world was William T. G. Morton.


The discovery of the anaesthetic power of drugs was destined

presently, in addition to its direct beneficences, to aid greatly

in the progress of scientific medicine, by facilitating those

experimental studies of animals from which, before the day of

anaesthesia, many humane physicians were withheld, and which in

recent years have led to discoveries of such inestimable value to

humanity. But for the moment this possibility was quite

overshadowed by the direct benefits of anaesthesia, and the long

strides that were taken in scientific medicine during the first

fifteen years after Morton's discovery were mainly independent of

such aid. These steps were taken, indeed, in a field that at

first glance might seem to have a very slight connection with

medicine. Moreover, the chief worker in the field was not himself

a physician. He was a chemist, and the work in which he was now

engaged was the study of alcoholic fermentation in vinous

liquors. Yet these studies paved the way for the most important

advances that medicine has made in any century towards the plane

of true science; and to this man more than to any other single

individual--it might almost be said more than to all other

individuals--was due this wonderful advance. It is almost

superfluous to add that the name of this marvellous chemist was

Louis Pasteur.

The studies of fermentation which Pasteur entered upon in 1854

were aimed at the solution of a controversy that had been waging

in the scientific world with varying degrees of activity for a

quarter of a century. Back in the thirties, in the day of the

early enthusiasm over the perfected microscope, there had arisen

a new interest in the minute forms of life which Leeuwenhoek and

some of the other early workers with the lens had first

described, and which now were shown to be of almost universal

prevalence. These minute organisms had been studied more or less

by a host of observers, but in particular by the Frenchman

Cagniard Latour and the German of cell-theory fame, Theodor

Schwann. These men, working independently, had reached the

conclusion, about 1837, that the micro-organisms play a vastly

more important role in the economy of nature than any one

previously had supposed. They held, for example, that the minute

specks which largely make up the substance of yeast are living

vegetable organisms, and that the growth of these organisms is

the cause of the important and familiar process of fermentation.

They even came to hold, at least tentatively, the opinion that

the somewhat similar micro-organisms to be found in all

putrefying matter, animal or vegetable, had a causal relation to

the process of putrefaction.

This view, particularly as to the nature of putrefaction, was

expressed even more outspokenly a little later by the French

botanist Turpin. Views so supported naturally gained a

following; it was equally natural that so radical an innovation

should be antagonized. In this case it chanced that one of the

most dominating scientific minds of the time, that of Liebig,

took a firm and aggressive stand against the new doctrine. In

1839 he promulgated his famous doctrine of fermentation, in which

he stood out firmly against any "vitalistic" explanation of the

phenomena, alleging that the presence of micro-organisms in

fermenting and putrefying substances was merely incidental, and

in no sense causal. This opinion of the great German chemist was

in a measure substantiated by experiments of his compatriot

Helmholtz, whose earlier experiments confirmed, but later ones

contradicted, the observations of Schwann, and this combined

authority gave the vitalistic conception a blow from which it had

not rallied at the time when Pasteur entered the field. Indeed,

it was currently regarded as settled that the early students of

the subject had vastly over-estimated the importance of


And so it came as a new revelation to the generality of

scientists of the time, when, in 1857 and the succeeding

half-decade, Pasteur published the results of his researches, in

which the question had been put to a series of altogether new

tests, and brought to unequivocal demonstration.

He proved that the micro-organisms do all that his most

imaginative predecessors had suspected, and more. Without them,

he proved, there would be no fermentation, no putrefaction--no

decay of any tissues, except by the slow process of oxidation. It

is the microscopic yeast-plant which, by seizing on certain atoms

of the molecule, liberates the remaining atoms in the form of

carbonic-acid and alcohol, thus effecting fermentation; it is

another microscopic plant--a bacterium, as Devaine had christened

it--which in a similar way effects the destruction of organic

molecules, producing the condition which we call putrefaction.

Pasteur showed, to the amazement of biologists, that there are

certain forms of these bacteria which secure the oxygen which all

organic life requires, not from the air, but by breaking up

unstable molecules in which oxygen is combined; that

putrefaction, in short, has its foundation in the activities of

these so-called anaerobic bacteria.

In a word, Pasteur showed that all the many familiar processes of

the decay of organic tissues are, in effect, forms of

fermentation, and would not take place at all except for the

presence of the living micro-organisms. A piece of meat, for

example, suspended in an atmosphere free from germs, will dry up

gradually, without the slightest sign of putrefaction, regardless

of the temperature or other conditions to which it may have been

subjected. Let us witness one or two series of these experiments

as presented by Pasteur himself in one of his numerous papers

before the Academy of Sciences.


"In the course of the discussion which took place before the

Academy upon the subject of the generation of ferments properly

so-called, there was a good deal said about that of wine, the

oldest fermentation known. On this account I decided to disprove

the theory of M. Fremy by a decisive experiment bearing solely

upon the juice of grapes.

"I prepared forty flasks of a capacity of from two hundred and

fifty to three hundred cubic centimetres and filled them half

full with filtered grape-must, perfectly clear, and which, as is

the case of all acidulated liquids that have been boiled for a

few seconds, remains uncontaminated although the curved neck of

the flask containing them remain constantly open during several

months or years.

"In a small quantity of water I washed a part of a bunch of

grapes, the grapes and the stalks together, and the stalks

separately. This washing was easily done by means of a small

badger's-hair brush. The washing-water collected the dust upon

the surface of the grapes and the stalks, and it was easily shown

under the microscope that this water held in suspension a

multitude of minute organisms closely resembling either fungoid

spores, or those of alcoholic Yeast, or those of Mycoderma vini,

etc. This being done, ten of the forty flasks were preserved for

reference; in ten of the remainder, through the straight tube

attached to each, some drops of the washing-water were

introduced; in a third series of ten flasks a few drops of the

same liquid were placed after it had been boiled; and, finally,

in the ten remaining flasks were placed some drops of grape-juice

taken from the inside of a perfect fruit. In order to carry out

this experiment, the straight tube of each flask was drawn out

into a fine and firm point in the lamp, and then curved. This

fine and closed point was filed round near the end and inserted

into the grape while resting upon some hard substance. When the

point was felt to touch the support of the grape it was by a

slight pressure broken off at the point file mark. Then, if care

had been taken to create a slight vacuum in the flask, a drop of

the juice of the grape got into it, the filed point was

withdrawn, and the aperture immediately closed in the alcohol

lamp. This decreased pressure of the atmosphere in the flask was

obtained by the following means: After warming the sides of the

flask either in the hands or in the lamp-flame, thus causing a

small quantity of air to be driven out of the end of the curved

neck, this end was closed in the lamp. After the flask was

cooled, there was a tendency to suck in the drop of grape-juice

in the manner just described.

"The drop of grape-juice which enters into the flask by this

suction ordinarily remains in the curved part of the tube, so

that to mix it with the must it was necessary to incline the

flask so as to bring the must into contact with the juice and

then replace the flask in its normal position. The four series of

comparative experiments produced the following results:

"The first ten flasks containing the grape-must boiled in pure

air did not show the production of any organism. The grape-must

could possibly remain in them for an indefinite number of years.

Those in the second series, containing the water in which the

grapes had been washed separately and together, showed without

exception an alcoholic fermentation which in several cases began

to appear at the end of forty-eight hours when the experiment

took place at ordinary summer temperature. At the same time that

the yeast appeared, in the form of white traces, which little by

little united themselves in the form of a deposit on the sides of

all the flasks, there were seen to form little flakes of

Mycellium, often as a single fungoid growth or in combination,

these fungoid growths being quite independent of the must or of

any alcoholic yeast. Often, also, the Mycoderma vini appeared

after some days upon the surface of the liquid. The Vibria and

the lactic ferments properly so called did not appear on account

of the nature of the liquid.

"The third series of flasks, the washing-water in which had been

previously boiled, remained unchanged, as in the first series.

Those of the fourth series, in which was the juice of the

interior of the grapes, remained equally free from change,

although I was not always able, on account of the delicacy of the

experiment, to eliminate every chance of error. These experiments

cannot leave the least doubt in the mind as to the following


Grape-must, after heating, never ferments on contact with the

air, when the air has been deprived of the germs which it

ordinarily holds in a state of suspension.

"The boiled grape-must ferments when there is introduced into it

a very small quantity of water in which the surface of the grapes

or their stalks have been washed.

"The grape-must does not ferment when this washing-water has been

boiled and afterwards cooled.

"The grape-must does not ferment when there is added to it a

small quantity of the juice of the inside of the grape.

"The yeast, therefore, which causes the fermentation of the

grapes in the vintage-tub comes from the outside and not from the

inside of the grapes. Thus is destroyed the hypothesis of MM.

Trecol and Fremy, who surmised that the albuminous matter

transformed itself into yeast on account of the vital germs which

were natural to it. With greater reason, therefore, there is no

longer any question of the theory of Liebig of the transformation

of albuminoid matter into ferments on account of the oxidation."


"The method which I have just followed," Pasteur continues, "in

order to show that there exists a correlation between the

diseases of beer and certain microscopic organisms leaves no room

for doubt, it seems to me, in regard to the principles I am


"Every time that the microscope reveals in the leaven, and

especially in the active yeast, the production of organisms

foreign to the alcoholic yeast properly so called, the flavor of

the beer leaves something to be desired, much or little,

according to the abundance and the character of these little

germs. Moreover, when a finished beer of good quality loses after

a time its agreeable flavor and becomes sour, it can be easily

shown that the alcoholic yeast deposited in the bottles or the

casks, although originally pure, at least in appearance, is found

to be contaminated gradually with these filiform or other

ferments. All this can be deduced from the facts already given,

but some critics may perhaps declare that these foreign ferments

are the consequences of the diseased condition, itself produced

by unknown causes.

"Although this gratuitous hypothesis may be difficult to uphold,

I will endeavor to corroborate the preceding observations by a

clearer method of investigation. This consists in showing that

the beer never has any unpleasant taste in all cases when the

alcoholic ferment properly so called is not mixed with foreign

ferments; that it is the same in the case of wort, and that wort,

liable to changes as it is, can be preserved unaltered if it is

kept from those microscopic parasites which find in it a suitable

nourishment and a field for growth.

"The employment of this second method has, moreover, the

advantage of proving with certainty the proposition that I

advanced at first--namely, that the germs of these organisms are

derived from the dust of the atmosphere, carried about and

deposited upon all objects, or scattered over the utensils and

the materials used in a brewery-materials naturally charged with

microscopic germs, and which the various operations in the

store-rooms and the malt-house may multiply indefinitely.

"Let us take a glass flask with a long neck of from two hundred

and fifty to three hundred cubic centimetres capacity, and place

in it some wort, with or without hops, and then in the flame of a

lamp draw out the neck of the flask to a fine point, afterwards

heating the liquid until the steam comes out of the end of the

neck. It can then be allowed to cool without any other

precautions; but for additional safety there can be introduced

into the little point a small wad of asbestos at the moment that

the flame is withdrawn from beneath the flask. Before thus

placing the asbestos it also can be passed through the flame, as

well as after it has been put into the end of the tube. The air

which then first re-enters the flask will thus come into contact

with the heated glass and the heated liquid, so as to destroy the

vitality of any dust germs that may exist in the air. The air

itself will re-enter very gradually, and slowly enough to enable

any dust to be taken up by the drop of water which the air forces

up the curvature of the tube. Ultimately the tube will be dry,

but the re-entering of the air will be so slow that the particles

of dust will fall upon the sides of the tube. The experiments

show that with this kind of vessel, allowing free communication

with the air, and the dust not being allowed to enter, the dust

will not enter at all events for a period of ten or twelve years,

which has been the longest period devoted to these trials; and

the liquid, if it were naturally limpid, will not be in the least

polluted neither on its surface nor in its mass, although the

outside of the flask may become thickly coated with dust. This is

a most irrefutable proof of the impossibility of dust getting

inside the flask.

"The wort thus prepared remains uncontaminated indefinitely, in

spite of its susceptibility to change when exposed to the air

under conditions which allow it to gather the dusty particles

which float in the atmosphere. It is the same in the case of

urine, beef-tea, and grape-must, and generally with all those

putrefactable and fermentable liquids which have the property

when heated to boiling-point of destroying the vitality of dust


There was nothing in these studies bearing directly upon the

question of animal diseases, yet before they were finished they

had stimulated progress in more than one field of pathology. At

the very outset they sufficed to start afresh the inquiry as to

the role played by micro-organisms in disease. In particular they

led the French physician Devaine to return to some interrupted

studies which he had made ten years before in reference to the

animal disease called anthrax, or splenic fever, a disease that

cost the farmers of Europe millions of francs annually through

loss of sheep and cattle. In 1850 Devaine had seen multitudes of

bacteria in the blood of animals who had died of anthrax, but he

did not at that time think of them as having a causal relation to

the disease. Now, however, in 1863, stimulated by Pasteur's new

revelations regarding the power of bacteria, he returned to the

subject, and soon became convinced, through experiments by means

of inoculation, that the microscopic organisms he had discovered

were the veritable and the sole cause of the infectious disease


The publication of this belief in 1863 aroused a furor of

controversy. That a microscopic vegetable could cause a virulent

systemic disease was an idea altogether too startling to be

accepted in a day, and the generality of biologists and

physicians demanded more convincing proofs than Devaine as yet

was able to offer.

Naturally a host of other investigators all over the world

entered the field. Foremost among these was the German Dr. Robert

Koch, who soon corroborated all that Devaine had observed, and

carried the experiments further in the direction of the

cultivation of successive generations of the bacteria in

artificial media, inoculations being made from such pure cultures

of the eighth generation, with the astonishing result that

animals thus inoculated succumbed to the disease.

Such experiments seem demonstrative, yet the world was

unconvinced, and in 1876, while the controversy was still at its

height, Pasteur was prevailed upon to take the matter in hand.

The great chemist was becoming more and more exclusively a

biologist as the years passed, and in recent years his famous

studies of the silk-worm diseases, which he proved due to

bacterial infection, and of the question of spontaneous

generation, had given him unequalled resources in microscopical

technique. And so when, with the aid of his laboratory associates

Duclaux and Chamberland and Roux, he took up the mooted anthrax

question the scientific world awaited the issue with bated

breath. And when, in 1877, Pasteur was ready to report on his

studies of anthrax, he came forward with such a wealth of

demonstrative experiments--experiments the rigid accuracy of

which no one would for a moment think of questioning--going to

prove the bacterial origin of anthrax, that scepticism was at

last quieted for all time to come.

Henceforth no one could doubt that the contagious disease anthrax

is due exclusively to the introduction into an animal's system of

a specific germ--a microscopic plant--which develops there. And

no logical mind could have a reasonable doubt that what is proved

true of one infectious disease would some day be proved true also

of other, perhaps of all, forms of infectious maladies.

Hitherto the cause of contagion, by which certain maladies spread

from individual to individual, had been a total mystery, quite

unillumined by the vague terms "miasm," "humor," "virus," and the

like cloaks of ignorance. Here and there a prophet of science,

as Schwann and Henle, had guessed the secret; but guessing, in

science, is far enough from knowing. Now, for the first time, the

world KNEW, and medicine had taken another gigantic stride

towards the heights of exact science.


Meantime, in a different though allied field of medicine there

had been a complementary growth that led to immediate results of

even more practical importance. I mean the theory and practice

of antisepsis in surgery. This advance, like the other, came as

a direct outgrowth of Pasteur's fermentation studies of alcoholic

beverages, though not at the hands of Pasteur himself. Struck by

the boundless implications of Pasteur's revelations regarding the

bacteria, Dr. Joseph Lister (the present Lord Lister), then of

Glasgow, set about as early as 1860 to make a wonderful

application of these ideas. If putrefaction is always due to

bacterial development, he argued, this must apply as well to

living as to dead tissues; hence the putrefactive changes which

occur in wounds and after operations on the human subject, from

which blood-poisoning so often follows, might be absolutely

prevented if the injured surfaces could be kept free from access

of the germs of decay.

In the hope of accomplishing this result, Lister began

experimenting with drugs that might kill the bacteria without

injury to the patient, and with means to prevent further access

of germs once a wound was freed from them. How well he succeeded

all the world knows; how bitterly he was antagonized for about a

score of years, most of the world has already forgotten. As early

as 1867 Lister was able to publish results pointing towards

success in his great project; yet so incredulous were surgeons in

general that even some years later the leading surgeons on the

Continent had not so much as heard of his efforts. In 1870 the

soldiers of Paris died, as of old, of hospital gangrene; and

when, in 1871, the French surgeon Alphonse Guerin, stimulated by

Pasteur's studies, conceived the idea of dressing wounds with

cotton in the hope of keeping germs from entering them, he was

quite unaware that a British contemporary had preceded him by a

full decade in this effort at prevention and had made long

strides towards complete success. Lister's priority, however, and

the superiority of his method, were freely admitted by the French

Academy of Sciences, which in 1881 officially crowned his

achievement, as the Royal Society of London had done the year


By this time, to be sure, as everybody knows, Lister's new

methods had made their way everywhere, revolutionizing the

practice of surgery and practically banishing from the earth

maladies that hitherto had been the terror of the surgeon and the

opprobrium of his art. And these bedside studies, conducted in

the end by thousands of men who had no knowledge of microscopy,

had a large share in establishing the general belief in the

causal relation that micro-organisms bear to disease, which by

about the year 1880 had taken possession of the medical world.

But they did more; they brought into equal prominence the idea

that, the cause of a diseased condition being known, it maybe

possible as never before to grapple with and eradicate that



The controversy over spontaneous generation, which, thanks to

Pasteur and Tyndall, had just been brought to a termination, made

it clear that no bacterium need be feared where an antecedent

bacterium had not found lodgment; Listerism in surgery had now

shown how much might be accomplished towards preventing the

access of germs to abraded surfaces of the body and destroying

those that already had found lodgment there. As yet, however,

there was no inkling of a way in which a corresponding onslaught

might be made upon those other germs which find their way into

the animal organism by way of the mouth and the nostrils, and

which, as was now clear, are the cause of those contagious

diseases which, first and last, claim so large a proportion of

mankind for their victims. How such means might be found now

became the anxious thought of every imaginative physician, of

every working microbiologist.

As it happened, the world was not kept long in suspense. Almost

before the proposition had taken shape in the minds of the other

leaders, Pasteur had found a solution. Guided by the empirical

success of Jenner, he, like many others, had long practised

inoculation experiments, and on February 9, 1880, he announced to

the French Academy of Sciences that he had found a method of so

reducing the virulence of a disease germ that when introduced

into the system of a susceptible animal it produced only a mild

form of the disease, which, however, sufficed to protect against

the usual virulent form exactly as vaccinia protects against

small-pox. The particular disease experimented with was that

infectious malady of poultry known familiarly as "chicken

cholera." In October of the same year Pasteur announced the

method by which this "attenuation of the virus," as he termed it,

had been brought about--by cultivation of the disease germs in

artificial media, exposed to the air, and he did not hesitate to

assert his belief that the method would prove "susceptible of

generalization"--that is to say, of application to other diseases

than the particular one in question.

Within a few months he made good this prophecy, for in February,

1881, he announced to the Academy that with the aid, as before,

of his associates MM. Chamberland and Roux, he had produced an

attenuated virus of the anthrax microbe by the use of which, as

he affirmed with great confidence, he could protect sheep, and

presumably cattle, against that fatal malady. "In some recent

publications," said Pasteur, "I announced the first case of the

attenuation of a virus by experimental methods only. Formed of a

special microbe of an extreme minuteness, this virus may be

multiplied by artificial culture outside the animal body. These

cultures, left alone without any possible external contamination,

undergo, in the course of time, modifications of their virulency

to a greater or less extent. The oxygen of the atmosphere is

said to be the chief cause of these attenuations--that is, this

lessening of the facilities of multiplication of the microbe; for

it is evident that the difference of virulence is in some way

associated with differences of development in the parasitic


"There is no need to insist upon the interesting character of

these results and the deductions to be made therefrom. To seek to

lessen the virulence by rational means would be to establish,

upon an experimental basis, the hope of preparing from an active

virus, easily cultivated either in the human or animal body, a

vaccine-virus of restrained development capable of preventing the

fatal effects of the former. Therefore, we have applied all our

energies to investigate the possible generalizing action of

atmospheric oxygen in the attenuation of virus.

"The anthrax virus, being one that has been most carefully

studied, seemed to be the first that should attract our

attention. Every time, however, we encountered a difficulty.

Between the microbe of chicken cholera and the microbe of anthrax

there exists an essential difference which does not allow the new

experiment to be verified by the old. The microbes of chicken

cholera do not, in effect, seem to resolve themselves, in their

culture, into veritable germs. The latter are merely cells, or

articulations always ready to multiply by division, except when

the particular conditions in which they become true germs are


"The yeast of beer is a striking example of these cellular

productions, being able to multiply themselves indefinitely

without the apparition of their original spores. There exist

many mucedines (Mucedinae?) of tubular mushrooms, which in

certain conditions of culture produce a chain of more or less

spherical cells called Conidae. The latter, detached from their

branches, are able to reproduce themselves in the form of cells,

without the appearance, at least with a change in the conditions

of culture, of the spores of their respective mucedines. These

vegetable organisms can be compared to plants which are

cultivated by slipping, and to produce which it is not necessary

to have the fruits or the seeds of the mother plant.

The anthrax bacterium, in its artificial cultivation, behaves

very differently. Its mycelian filaments, if one may so describe

them, have been produced scarcely for twenty-four or forty-eight

hours when they are seen to transform themselves, those

especially which are in free contact with the air, into very

refringent corpuscles, capable of gradually isolating themselves

into true germs of slight organization. Moreover, observation

shows that these germs, formed so quickly in the culture, do not

undergo, after exposure for a time to atmospheric air, any change

either in their vitality or their virulence. I was able to

present to the Academy a tube containing some spores of anthrax

bacteria produced four years ago, on March 21, 1887. Each year

the germination of these little corpuscles has been tried, and

each year the germination has been accomplished with the same

facility and the same rapidity as at first. Each year also the

virulence of the new cultures has been tested, and they have not

shown any visible falling off. Therefore, how can we experiment

with the action of the air upon the anthrax virus with any

expectation of making it less virulent?

"The crucial difficulty lies perhaps entirely in this rapid

reproduction of the bacteria germs which we have just related. In

its form of a filament, and in its multiplication by division, is

not this organism at all points comparable with the microbe of

the chicken cholera?

"That a germ, properly so called, that a seed, does not suffer

any modification on account of the air is easily conceived; but

it is conceivable not less easily that if there should be any

change it would occur by preference in the case of a mycelian

fragment. It is thus that a slip which may have been abandoned in

the soil in contact with the air does not take long to lose all

vitality, while under similar conditions a seed is preserved in

readiness to reproduce the plant. If these views have any

foundation, we are led to think that in order to prove the action

of the air upon the anthrax bacteria it will be indispensable to

submit to this action the mycelian development of the minute

organism under conditions where there cannot be the least

admixture of corpuscular germs. Hence the problem of submitting

the bacteria to the action of oxygen comes back to the question

of presenting entirely the formation of spores. The question

being put in this way, we are beginning to recognize that it is

capable of being solved.

"We can, in fact, prevent the appearance of spores in the

artificial cultures of the anthrax parasite by various artifices.

At the lowest temperature at which this parasite can be

cultivated--that is to say, about +16 degrees Centigrade--the

bacterium does not produce germs--at any rate, for a very long

time. The shapes of the minute microbe at this lowest limit of

its development are irregular, in the form of balls and pears--in

a word, they are monstrosities--but they are without spores. In

the last regard also it is the same at the highest temperatures

at which the parasite can be cultivated, temperatures which vary

slightly according to the means employed. In neutral chicken

bouillon the bacteria cannot be cultivated above 45 degrees.

Culture, however, is easy and abundant at 42 to 43 degrees, but

equally without any formation of spores. Consequently a culture

of mycelian bacteria can be kept entirely free from germs while

in contact with the open air at a temperature of from 42 to 43

degrees Centigrade. Now appear the three remarkable results.

After about one month of waiting the culture dies--that is to

say, if put into a fresh bouillon it becomes absolutely sterile.

"So much for the life and nutrition of this organism. In respect

to its virulence, it is an extraordinary fact that it disappears

entirely after eight days' culture at 42 to 43 degrees

Centigrade, or, at any rate, the cultures are innocuous for the

guinea-pig, the rabbit, and the sheep, the three kinds of animals

most apt to contract anthrax. We are thus able to obtain, not

only the attenuation of the virulence, but also its complete

suppression by a simple method of cultivation. Moreover, we see

also the possibility of preserving and cultivating the terrible

microbe in an inoffensive state. What is it that happens in these

eight days at 43 degrees that suffices to take away the virulence

of the bacteria? Let us remember that the microbe of chicken

cholera dies in contact with the air, in a period somewhat

protracted, it is true, but after successive attenuations. Are

we justified in thinking that it ought to be the same in regard

to the microbe of anthrax? This hypothesis is confirmed by

experiment. Before the disappearance of its virulence the anthrax

microbe passes through various degrees of attenuation, and,

moreover, as is also the case with the microbe of chicken

cholera, each of these attenuated states of virulence can be

obtained by cultivation. Moreover, since, according to one of our

recent Communications, anthrax is not recurrent, each of our

attenuated anthrax microbes is, for the better-developed microbe,

a vaccine--that is to say, a virus producing a less-malignant

malady. What, therefore, is easier than to find in these a virus

that will infect with anthrax sheep, cows, and horses, without

killing them, and ultimately capable of warding off the mortal

malady? We have practised this experiment with great success upon

sheep, and when the season comes for the assembling of the flocks

at Beauce we shall try the experiment on a larger scale.

"Already M. Toussaint has announced that sheep can be saved by

preventive inoculations; but when this able observer shall have

published his results; on the subject of which we have made such

exhaustive studies, as yet unpublished, we shall be able to see

the whole difference which exists between the two methods--the

uncertainty of the one and the certainty of the other. That which

we announce has, moreover, the very great advantage of resting

upon the existence of a poison vaccine cultivable at will, and

which can be increased indefinitely in the space of a few hours

without having recourse to infected blood."[8]

This announcement was immediately challenged in a way that

brought it to the attention of the entire world. The president of

an agricultural society, realizing the enormous importance of the

subject, proposed to Pasteur that his alleged discovery should be

submitted to a decisive public test. He proposed to furnish a

drove of fifty sheep half of which were to be inoculated with the

attenuated virus of Pasteur. Subsequently all the sheep were to

be inoculated with virulent virus, all being kept together in one

pen under precisely the same conditions. The "protected" sheep

were to remain healthy; the unprotected ones to die of anthrax;

so read the terms of the proposition. Pasteur accepted the

challenge; he even permitted a change in the programme by which

two goats were substituted for two of the sheep, and ten cattle

added, stipulating, however, that since his experiments had not

yet been extended to cattle these should not be regarded as

falling rigidly within the terms of the test.

It was a test to try the soul of any man, for all the world

looked on askance, prepared to deride the maker of so

preposterous a claim as soon as his claim should be proved

baseless. Not even the fame of Pasteur could make the public at

large, lay or scientific, believe in the possibility of what he

proposed to accomplish. There was time for all the world to be

informed of the procedure, for the first "preventive"

inoculation--or vaccination, as Pasteur termed it--was made on

May 5th, the second on May 17th, and another interval of two

weeks must elapse before the final inoculations with the

unattenuated virus. Twenty-four sheep, one goat, and five cattle

were submitted to the preliminary vaccinations. Then, on May 31

st, all sixty of the animals were inoculated, a protected and

unprotected one alternately, with an extremely virulent culture

of anthrax microbes that had been in Pasteur's laboratory since

1877. This accomplished, the animals were left together in one

enclosure to await the issue.

Two days later, June 2d, at the appointed hour of rendezvous, a

vast crowd, composed of veterinary surgeons, newspaper

correspondents, and farmers from far and near, gathered to

witness the closing scenes of this scientific tourney. What they

saw was one of the most dramatic scenes in the history of

peaceful science--a scene which, as Pasteur declared afterwards,

"amazed the assembly." Scattered about the enclosure, dead,

dying, or manifestly sick unto death, lay the unprotected

animals, one and all, while each and every "protected" animal

stalked unconcernedly about with every appearance of perfect

health. Twenty of the sheep and the one goat were already dead;

two other sheep expired under the eyes of the spectators; the

remaining victims lingered but a few hours longer. Thus in a

manner theatrical enough, not to say tragic, was proclaimed the

unequivocal victory of science. Naturally enough, the unbelievers

struck their colors and surrendered without terms; the principle

of protective vaccination, with a virus experimentally prepared

in the laboratory, was established beyond the reach of


That memorable scientific battle marked the beginning of a new

era in medicine. It was a foregone conclusion that the principle

thus established would be still further generalized; that it

would be applied to human maladies; that in all probability it

would grapple successfully, sooner or later, with many infectious

diseases. That expectation has advanced rapidly towards

realization. Pasteur himself made the application to the human

subject in the disease hydrophobia in 1885, since which time that

hitherto most fatal of maladies has largely lost its terrors.

Thousands of persons bitten by mad dogs have been snatched from

the fatal consequences of that mishap by this method at the

Pasteur Institute in Paris, and at the similar institutes, built

on the model of this parent one, that have been established all

over the world in regions as widely separated as New York and



In the production of the rabies vaccine Pasteur and his

associates developed a method of attenuation of a virus quite

different from that which had been employed in the case of the

vaccines of chicken cholera and of anthrax. The rabies virus was

inoculated into the system of guinea-pigs or rabbits and, in

effect, cultivated in the systems of these animals. The spinal

cord of these infected animals was found to be rich in the virus,

which rapidly became attenuated when the cord was dried in the

air. The preventive virus, of varying strengths, was made by

maceration of these cords at varying stages of desiccation. This

cultivation of a virus within the animal organism suggested, no

doubt, by the familiar Jennerian method of securing small-pox

vaccine, was at the same time a step in the direction of a new

therapeutic procedure which was destined presently to become of

all-absorbing importance--the method, namely, of so-called

serum-therapy, or the treatment of a disease with the blood serum

of an animal that has been subjected to protective inoculation

against that disease.

The possibility of such a method was suggested by the familiar

observation, made by Pasteur and numerous other workers, that

animals of different species differ widely in their

susceptibility to various maladies, and that the virus of a given

disease may become more and more virulent when passed through the

systems of successive individuals of one species, and,

contrariwise, less and less virulent when passed through the

systems of successive individuals of another species. These facts

suggested the theory that the blood of resistant animals might

contain something directly antagonistic to the virus, and the

hope that this something might be transferred with curative

effect to the blood of an infected susceptible animal. Numerous

experimenters all over the world made investigations along the

line of this alluring possibility, the leaders perhaps being Drs.

Behring and Kitasato, closely followed by Dr. Roux and his

associates of the Pasteur Institute of Paris. Definite results

were announced by Behring in 1892 regarding two important

diseases--tetanus and diphtheria--but the method did not come

into general notice until 1894, when Dr. Roux read an

epoch-making paper on the subject at the Congress of Hygiene at


In this paper Dr. Roux, after adverting to the labors of Behring,

Ehrlich, Boer, Kossel, and Wasserman, described in detail the

methods that had been developed at the Pasteur Institute for the

development of the curative serum, to which Behring had given the

since-familiar name antitoxine. The method consists, first, of

the cultivation, for some months, of the diphtheria bacillus

(called the Klebs-Loeffler bacillus, in honor of its discoverers)

in an artificial bouillon, for the development of a powerful

toxine capable of giving the disease in a virulent form.

This toxine, after certain details of mechanical treatment, is

injected in small but increasing doses into the system of an

animal, care being taken to graduate the amount so that the

animal does not succumb to the disease. After a certain course of

this treatment it is found that a portion of blood serum of the

animal so treated will act in a curative way if injected into the

blood of another animal, or a human patient, suffering with

diphtheria. In other words, according to theory, an antitoxine

has been developed in the system of the animal subjected to the

progressive inoculations of the diphtheria toxine. In Dr. Roux's

experience the animal best suited for the purpose is the horse,

though almost any of the domesticated animals will serve the


But Dr. Roux's paper did not stop with the description of

laboratory methods. It told also of the practical application of

the serum to the treatment of numerous cases of diphtheria in the

hospitals of Paris--applications that had met with a gratifying

measure of success. He made it clear that a means had been found

of coping successfully with what had been one of the most

virulent and intractable of the diseases of childhood. Hence it

was not strange that his paper made a sensation in all circles,

medical and lay alike.

Physicians from all over the world flocked to Paris to learn the

details of the open secret, and within a few months the new

serum-therapy had an acknowledged standing with the medical

profession everywhere. What it had accomplished was regarded as

but an earnest of what the new method might accomplish presently

when applied to the other infectious diseases.

Efforts at such applications were immediately begun in numberless

directions--had, indeed, been under way in many a laboratory for

some years before. It is too early yet to speak of the results in

detail. But enough has been done to show that this method also is

susceptible of the widest generalization. It is not easy at the

present stage to sift that which is tentative from that which

will be permanent; but so great an authority as Behring does not

hesitate to affirm that today we possess, in addition to the

diphtheria antitoxine, equally specific antitoxines of tetanus,

cholera, typhus fever, pneumonia, and tuberculosis--a set of

diseases which in the aggregate account for a startling

proportion of the general death-rate. Then it is known that Dr.

Yersin, with the collaboration of his former colleagues of the

Pasteur Institute, has developed, and has used with success, an

antitoxine from the microbe of the plague which recently ravaged


Dr. Calmette, another graduate of the Pasteur Institute, has

extended the range of the serum-therapy to include the prevention

and treatment of poisoning by venoms, and has developed an

antitoxine that has already given immunity from the lethal

effects of snake bites to thousands of persons in India and


Just how much of present promise is tentative, just what are the

limits of the methods--these are questions for the future to

decide. But, in any event, there seems little question that the

serum treatment will stand as the culminating achievement in

therapeutics of our century. It is the logical outgrowth of those

experimental studies with the microscope begun by our

predecessors of the thirties, and it represents the present

culmination of the rigidly experimental method which has brought

medicine from a level of fanciful empiricism to the plane of a

rational experimental science.



A little over a hundred years ago a reform movement was afoot in

the world in the interests of the insane. As was fitting, the

movement showed itself first in America, where these unfortunates

were humanely cared for at a time when their treatment elsewhere

was worse than brutal; but England and France quickly fell into

line. The leader on this side of the water was the famous

Philadelphian, Dr. Benjamin Rush, "the Sydenham of America"; in

England, Dr. William Tuke inaugurated the movement; and in

France, Dr. Philippe Pinel, single-handed, led the way. Moved by

a common spirit, though acting quite independently, these men

raised a revolt against the traditional custom which, spurning

the insane as demon-haunted outcasts, had condemned these

unfortunates to dungeons, chains, and the lash. Hitherto few

people had thought it other than the natural course of events

that the "maniac" should be thrust into a dungeon, and perhaps

chained to the wall with the aid of an iron band riveted

permanently about his neck or waist. Many an unfortunate, thus

manacled, was held to the narrow limits of his chain for years

together in a cell to which full daylight never penetrated;

sometimes--iron being expensive--the chain was so short that the

wretched victim could not rise to the upright posture or even

shift his position upon his squalid pallet of straw.

In America, indeed, there being no Middle Age precedents to

crystallize into established customs, the treatment accorded the

insane had seldom or never sunk to this level. Partly for this

reason, perhaps, the work of Dr. Rush at the Philadelphia

Hospital, in 1784, by means of which the insane came to be

humanely treated, even to the extent of banishing the lash, has

been but little noted, while the work of the European leaders,

though belonging to later decades, has been made famous. And

perhaps this is not as unjust as it seems, for the step which

Rush took, from relatively bad to good, was a far easier one to

take than the leap from atrocities to good treatment which the

European reformers were obliged to compass. In Paris, for

example, Pinel was obliged to ask permission of the authorities

even to make the attempt at liberating the insane from their

chains, and, notwithstanding his recognized position as a leader

of science, he gained but grudging assent, and was regarded as

being himself little better than a lunatic for making so

manifestly unwise and hopeless an attempt. Once the attempt had

been made, however, and carried to a successful issue, the

amelioration wrought in the condition of the insane was so patent

that the fame of Pinel's work at the Bicetre and the Salpetriere

went abroad apace. It required, indeed, many years to complete it

in Paris, and a lifetime of effort on the part of Pinel's pupil

Esquirol and others to extend the reform to the provinces; but

the epochal turning-point had been reached with Pinel's labors of

the closing years of the eighteenth century.

The significance of this wise and humane reform, in the present

connection, is the fact that these studies of the insane gave

emphasis to the novel idea, which by-and-by became accepted as

beyond question, that "demoniacal possession" is in reality no

more than the outward expression of a diseased condition of the

brain. This realization made it clear, as never before, how

intimately the mind and the body are linked one to the other.

And so it chanced that, in striking the shackles from the insane,

Pinel and his confreres struck a blow also, unwittingly, at

time-honored philosophical traditions. The liberation of the

insane from their dungeons was an augury of the liberation of

psychology from the musty recesses of metaphysics. Hitherto

psychology, in so far as it existed at all, was but the

subjective study of individual minds; in future it must become

objective as well, taking into account also the relations which

the mind bears to the body, and in particular to the brain and

nervous system.

The necessity for this collocation was advocated quite as

earnestly, and even more directly, by another worker of this

period, whose studies were allied to those of alienists, and who,

even more actively than they, focalized his attention upon the

brain and its functions. This earliest of specialists in brain

studies was a German by birth but Parisian by adoption, Dr. Franz

Joseph Gall, originator of the since-notorious system of

phrenology. The merited disrepute into which this system has

fallen through the exposition of peripatetic charlatans should

not make us forget that Dr. Gall himself was apparently a highly

educated physician, a careful student of the brain and mind

according to the best light of his time, and, withal, an earnest

and honest believer in the validity of the system he had

originated. The system itself, taken as a whole, was hopelessly

faulty, yet it was not without its latent germ of truth, as later

studies were to show. How firmly its author himself believed in

it is evidenced by the paper which he contributed to the French

Academy of Sciences in 1808. The paper itself was referred to a

committee of which Pinel and Cuvier were members. The verdict of

this committee was adverse, and justly so; yet the system

condemned had at least one merit which its detractors failed to

realize. It popularized the conception that the brain is the

organ of mind. Moreover, by its insistence it rallied about it a

band of scientific supporters, chief of whom was Dr. Kaspar

Spurzlieim, a man of no mean abilities, who became the

propagandist of phrenology in England and in America. Of course

such advocacy and popularity stimulated opposition as well, and

out of the disputations thus arising there grew presently a

general interest in the brain as the organ of mind, quite aside

from any preconceptions whatever as to the doctrines of Gall and


Prominent among the unprejudiced class of workers who now

appeared was the brilliant young Frenchman Louis Antoine

Desmoulins, who studied first under the tutorage of the famous

Magendie, and published jointly with him a classical work on the

nervous system of vertebrates in 1825. Desmoulins made at least

one discovery of epochal importance. He observed that the brains

of persons dying in old age were lighter than the average and

gave visible evidence of atrophy, and he reasoned that such decay

is a normal accompaniment of senility. No one nowadays would

question the accuracy of this observation, but the scientific

world was not quite ready for it in 1825; for when Desmoulins

announced his discovery to the French Academy, that august and

somewhat patriarchal body was moved to quite unscientific wrath,

and forbade the young iconoclast the privilege of further

hearings. From which it is evident that the partially liberated

spirit of the new psychology had by no means freed itself

altogether, at the close of the first quarter of the nineteenth

century, from the metaphysical cobwebs of its long incarceration.


While studies of the brain were thus being inaugurated, the

nervous system, which is the channel of communication between the

brain and the outside world, was being interrogated with even

more tangible results. The inaugural discovery was made in 1811

by Dr. (afterwards Sir Charles) Bell,[1] the famous English

surgeon and experimental physiologist. It consisted of the

observation that the anterior roots of the spinal nerves are

given over to the function of conveying motor impulses from the

brain outward, whereas the posterior roots convey solely sensory

impulses to the brain from without. Hitherto it had been supposed

that all nerves have a similar function, and the peculiar

distribution of the spinal nerves had been an unsolved puzzle.

Bell's discovery was epochal; but its full significance was not

appreciated for a decade, nor, indeed, was its validity at first

admitted. In Paris, in particular, then the court of final

appeal in all matters scientific, the alleged discovery was

looked at askance, or quite ignored. But in 1823 the subject was

taken up by the recognized leader of French physiology--Francois

Magendie--in the course of his comprehensive experimental studies

of the nervous system, and Bell's conclusions were subjected to

the most rigid experimental tests and found altogether valid.

Bell himself, meanwhile, had turned his attention to the cranial

nerves, and had proved that these also are divisible into two

sets--sensory and motor. Sometimes, indeed, the two sets of

filaments are combined into one nerve cord, but if traced to

their origin these are found to arise from different brain

centres. Thus it was clear that a hitherto unrecognized duality

of function pertains to the entire extra-cranial nervous system.

Any impulse sent from the periphery to the brain must be conveyed

along a perfectly definite channel; the response from the brain,

sent out to the peripheral muscles, must traverse an equally

definite and altogether different course. If either channel is

interrupted--as by the section of its particular nerve tract--the

corresponding message is denied transmission as effectually as an

electric current is stopped by the section of the transmitting


Experimenters everywhere soon confirmed the observations of Bell

and Magendie, and, as always happens after a great discovery, a

fresh impulse was given to investigations in allied fields.

Nevertheless, a full decade elapsed before another discovery of

comparable importance was made. Then Marshall Hall, the most

famous of English physicians of his day, made his classical

observations on the phenomena that henceforth were to be known as

reflex action. In 1832, while experimenting one day with a

decapitated newt, he observed that the headless creature's limbs

would contract in direct response to certain stimuli. Such a

response could no longer be secured if the spinal nerves

supplying a part were severed. Hence it was clear that responsive

centres exist in the spinal cord capable of receiving a sensory

message and of transmitting a motor impulse in reply--a function

hitherto supposed to be reserved for the brain. Further studies

went to show that such phenomena of reflex action on the part of

centres lying outside the range of consciousness, both in the

spinal cord and in the brain itself, are extremely common; that,

in short, they enter constantly into the activities of every

living organism and have a most important share in the sum total

of vital movements. Hence, Hall's discovery must always stand as

one of the great mile-stones of the advance of neurological


Hall gave an admirably clear and interesting account of his

experiments and conclusions in a paper before the Royal Society,

"On the Reflex Functions of the Medulla Oblongata and the Medulla

Spinalis," from which, as published in the Transactions of the

society for 1833, we may quote at some length:

"In the entire animal, sensation and voluntary motion, functions

of the cerebrum, combine with the functions of the medulla

oblongata and medulla spinalis, and may therefore render it

difficult or impossible to determine those which are peculiar to

each; if, in an animal deprived of the brain, the spinal marrow

or the nerves supplying the muscles be stimulated, those muscles,

whether voluntary or respiratory, are equally thrown into

contraction, and, it may be added, equally in the complete and in

the mutilated animal; and, in the case of the nerves, equally in

limbs connected with and detached from the spinal marrow.

"The operation of all these various causes may be designated

centric, as taking place AT, or at least in a direction FROM,

central parts of the nervous system. But there is another

function the phenomena of which are of a totally different order

and obey totally different laws, being excited by causes in a

situation which is EXCENTRIC in the nervous system--that is,

distant from the nervous centres. This mode of action has not, I

think, been hitherto distinctly understood by physiologists.

"Many of the phenomena of this principle of action, as they occur

in the limbs, have certainly been observed. But, in the first

place, this function is by no means confined to the limbs; for,

while it imparts to each muscle its appropriate tone, and to each

system of muscles its appropriate equilibrium or balance, it

performs the still more important office of presiding over the

orifices and terminations of each of the internal canals in the

animal economy, giving them their due form and action; and, in

the second place, in the instances in which the phenomena of this

function have been noticed, they have been confounded, as I have

stated, with those of sensation and volition; or, if they have

been distinguished from these, they have been too indefinitely

denominated instinctive, or automatic. I have been compelled,

therefore, to adopt some new designation for them, and I shall

now give the reasons for my choice of that which is given in the

title of this paper--'Reflex Functions.'

"This property is characterized by being EXCITED in its action

and REFLEX in its course: in every instance in which it is

exerted an impression made upon the extremities of certain nerves

is conveyed to the medulla oblongata or the medulla spinalis, and

is reflected along the nerves to parts adjacent to, or remote

from, that which has received the impression.

"It is by this reflex character that the function to which I have

alluded is to be distinguished from every other. There are, in

the animal economy, four modes of muscular action, of muscular

contraction. The first is that designated VOLUNTARY: volition,

originated in the cerebrum and spontaneous in its acts, extends

its influence along the spinal marrow and the motor nerves in a

DIRECT LINE to the voluntary muscles. The SECOND is that of

RESPIRATION: like volition, the motive influence in respiration

passes in a DIRECT LINE from one point of the nervous system to

certain muscles; but as voluntary motion seems to originate in

the cerebrum, so the respiratory motions originate in the medulla

oblongata: like the voluntary motions, the motions of

respirations are spontaneous; they continue, at least, after the

eighth pair of nerves have been divided. The THIRD kind of

muscular action in the animal economy is that termed involuntary:

it depends upon the principle of irritability and requires the

IMMEDIATE application of a stimulus to the nervo-muscular fibre

itself. These three kinds of muscular motion are well known to

physiologists; and I believe they are all which have been

hitherto pointed out. There is, however, a FOURTH, which

subsists, in part, after the voluntary and respiratory motions

have ceased, by the removal of the cerebrum and medulla

oblongata, and which is attached to the medulla spinalis, ceasing

itself when this is removed, and leaving the irritability

undiminished. In this kind of muscular motion the motive

influence does not originate in any central part of the nervous

system, but from a distance from that centre; it is neither

spontaneous in its action nor direct in its course; it is, on the

contrary, EXCITED by the application of appropriate stimuli,

which are not, however, applied immediately to the muscular or

nervo-muscular fibre, but to certain membraneous parts, whence

the impression is carried through the medulla, REFLECTED and

reconducted to the part impressed, or conducted to a part remote

from it in which muscular contraction is effected.

"The first three modes of muscular action are known only by

actual movements of muscular contractions. But the reflex

function exists as a continuous muscular action, as a power

presiding over organs not actually in a state of motion,

preserving in some, as the glottis, an open, in others, as the

sphincters, a closed form, and in the limbs a due degree of

equilibrium or balanced muscular action--a function not, I think,

hitherto recognized by physiologists.

The three kinds of muscular motion hitherto known may be

distinguished in another way. The muscles of voluntary motion

and of respiration may be excited by stimulating the nerves which

supply them, in any part of their course, whether at their source

as a part of the medulla oblongata or the medulla spinalis or

exterior to the spinal canal: the muscles of involuntary motion

are chiefly excited by the actual contact of stimuli. In the

case of the reflex function alone the muscles are excited by a

stimulus acting mediately and indirectly in a curved and reflex

course, along superficial subcutaneous or submucous nerves

proceeding from the medulla. The first three of these causes of

muscular motion may act on detached limbs or muscles. The last

requires the connection with the medulla to be preserved entire.

"All the kinds of muscular motion may be unduly excited, but the

reflex function is peculiar in being excitable in two modes of

action, not previously subsisting in the animal economy, as in

the case of sneezing, coughing, vomiting, etc. The reflex

function also admits of being permanently diminished or augmented

and of taking on some other morbid forms, of which I shall treat


"Before I proceed to the details of the experiments upon which

this disposition rests, it may be well to point out several

instances in illustration of the various sources of and the modes

of muscular action which have been enumerated. None can be more

familiar than the act of swallowing. Yet how complicated is the

act! The apprehension of the food by the teeth and tongue, etc.,

is voluntary, and cannot, therefore, take place in an animal from

which the cerebrum is removed. The transition of food over the

glottis and along the middle and lower part of the pharynx

depends upon the reflex action: it can take place in animals from

which the cerebrum has been removed or the ninth pair of nerves

divided; but it requires the connection with the medulla

oblongata to be preserved entirely; and the actual contact of

some substance which may act as a stimulus: it is attended by

the accurate closure of the glottis and by the contraction of the

pharynx. The completion of the act of deglutition is dependent

upon the stimulus immediately impressed upon the muscular fibre

of the oesophagus, and is the result of excited irritability.

"However plain these observations may have made the fact that

there is a function of the nervous muscular system distinct from

sensation, from the voluntary and respiratory motions, and from

irritability, it is right, in every such inquiry as the present,

that the statements and reasonings should be made with the

experiment, as it were, actually before us. It has already been

remarked that the voluntary and respiratory motions are

spontaneous, not necessarily requiring the agency of a stimulus.

If, then, an animal can be placed in such circumstances that such

motions will certainly not take place, the power of moving

remaining, it may be concluded that volition and the motive

influence of respiration are annihilated. Now this is effected by

removing the cerebrum and the medulla oblongata. These facts are

fully proved by the experiments of Legallois and M. Flourens, and

by several which I proceed to detail, for the sake of the

opportunity afforded by doing so of stating the arguments most


"I divided the spinal marrow of a very lively snake between the

second and third vertebrae. The movements of the animal were

immediately before extremely vigorous and unintermitted. From the

moment of the division of the spinal marrow it lay perfectly

tranquil and motionless, with the exception of occasional

gaspings and slight movements of the head. It became quite

evident that this state of quiescence would continue indefinitely

were the animal secured from all external impressions.

"Being now stimulated, the body began to move with great

activity, and continued to do so for a considerable time, each

change of position or situation bringing some fresh part of the

surface of the animal into contact with the table or other

objects and renewing the application of stimulants.

"At length the animal became again quiescent; and being carefully

protected from all external impressions it moved no more, but

died in the precise position and form which it had last assumed.

"It requires a little manoeuvre to perform this experiment

successfully: the motions of the animal must be watched and

slowly and cautiously arrested by opposing some soft substance,

as a glove or cotton wool; they are by this means gradually

lulled into quiescence. The slightest touch with a hard

substance, the slightest stimulus, will, on the other hand, renew

the movements on the animal in an active form. But that this

phenomenon does not depend upon sensation is further fully proved

by the facts that the position last assumed, and the stimuli, may

be such as would be attended by extreme or continued pain, if the

sensibility were undestroyed: in one case the animal remained

partially suspended over the acute edge of the table; in others

the infliction of punctures and the application of a lighted

taper did not prevent the animal, still possessed of active

powers of motion, from passing into a state of complete and

permanent quiescence."

In summing up this long paper Hall concludes with this sentence:

"The reflex function appears in a word to be the COMPLEMENT of

the functions of the nervous system hitherto known."[2]

All these considerations as to nerve currents and nerve tracts

becoming stock knowledge of science, it was natural that interest

should become stimulated as to the exact character of these nerve

tracts in themselves, and all the more natural in that the

perfected microscope was just now claiming all fields for its

own. A troop of observers soon entered upon the study of the

nerves, and the leader here, as in so many other lines of

microscopical research, was no other than Theodor Schwann.

Through his efforts, and with the invaluable aid of such other

workers as Remak, Purkinje, Henle, Muller, and the rest, all the

mystery as to the general characteristics of nerve tracts was

cleared away. It came to be known that in its essentials a nerve

tract is a tenuous fibre or thread of protoplasm stretching

between two terminal points in the organism, one of such termini

being usually a cell of the brain or spinal cord, the other a

distribution-point at or near the periphery--for example, in a

muscle or in the skin. Such a fibril may have about it a

protective covering, which is known as the sheath of Schwann; but

the fibril itself is the essential nerve tract; and in many

cases, as Remak presently discovered, the sheath is dispensed

with, particularly in case of the nerves of the so-called

sympathetic system.

This sympathetic system of ganglia and nerves, by-the-bye, had

long been a puzzle to the physiologists. Its ganglia, the

seeming centre of the system, usually minute in size and never

very large, are found everywhere through the organism, but in

particular are gathered into a long double chain which lies

within the body cavity, outside the spinal column, and represents

the sole nervous system of the non-vertebrated organisms. Fibrils

from these ganglia were seen to join the cranial and spinal nerve

fibrils and to accompany them everywhere, but what special

function they subserved was long a mere matter of conjecture and

led to many absurd speculations. Fact was not substituted for

conjecture until about the year 1851, when the great Frenchman

Claude Bernard conclusively proved that at least one chief

function of the sympathetic fibrils is to cause contraction of

the walls of the arterioles of the system, thus regulating the

blood-supply of any given part. Ten years earlier Henle had

demonstrated the existence of annular bands of muscle fibres in

the arterioles, hitherto a much-mooted question, and several

tentative explanations of the action of these fibres had been

made, particularly by the brothers Weber, by Stilling, who, as

early as 1840, had ventured to speak of "vaso-motor" nerves, and

by Schiff, who was hard upon the same track at the time of

Bernard's discovery. But a clear light was not thrown on the

subject until Bernard's experiments were made in 1851. The

experiments were soon after confirmed and extended by

Brown-Sequard, Waller, Budge, and numerous others, and henceforth

physiologists felt that they understood how the blood-supply of

any given part is regulated by the nervous system.

In reality, however, they had learned only half the story, as

Bernard himself proved only a few years later by opening up a new

and quite unsuspected chapter. While experimenting in 1858 he

discovered that there are certain nerves supplying the heart

which, if stimulated, cause that organ to relax and cease

beating. As the heart is essentially nothing more than an

aggregation of muscles, this phenomenon was utterly puzzling and

without precedent in the experience of physiologists. An impulse

travelling along a motor nerve had been supposed to be able to

cause a muscular contraction and to do nothing else; yet here

such an impulse had exactly the opposite effect. The only tenable

explanation seemed to be that this particular impulse must arrest

or inhibit the action of the impulses that ordinarily cause the

heart muscles to contract. But the idea of such inhibition of one

impulse by another was utterly novel and at first difficult to

comprehend. Gradually, however, the idea took its place in the

current knowledge of nerve physiology, and in time it came to be

understood that what happens in the case of the heart

nerve-supply is only a particular case under a very general,

indeed universal, form of nervous action. Growing out of

Bernard's initial discovery came the final understanding that the

entire nervous system is a mechanism of centres subordinate and

centres superior, the action of the one of which may be

counteracted and annulled in effect by the action of the other.

This applies not merely to such physical processes as heart-beats

and arterial contraction and relaxing, but to the most intricate

functionings which have their counterpart in psychical processes

as well. Thus the observation of the inhibition of the heart's

action by a nervous impulse furnished the point of departure for

studies that led to a better understanding of the modus operandi

of the mind's activities than had ever previously been attained

by the most subtle of psychologists.


The work of the nerve physiologists had thus an important bearing

on questions of the mind. But there was another company of

workers of this period who made an even more direct assault upon

the "citadel of thought." A remarkable school of workers had been

developed in Germany, the leaders being men who, having more or

less of innate metaphysical bias as a national birthright, had

also the instincts of the empirical scientist, and whose

educational equipment included a profound knowledge not alone of

physiology and psychology, but of physics and mathematics as

well. These men undertook the novel task of interrogating the

relations of body and mind from the standpoint of physics. They

sought to apply the vernier and the balance, as far as might be,

to the intangible processes of mind.

The movement had its precursory stages in the early part of the

century, notably in the mathematical psychology of Herbart, but

its first definite output to attract general attention came from

the master-hand of Hermann Helmholtz in 1851. It consisted of the

accurate measurement of the speed of transit of a nervous impulse

along a nerve tract. To make such measurement had been regarded

as impossible, it being supposed that the flight of the nervous

impulse was practically instantaneous. But Helmholtz readily

demonstrated the contrary, showing that the nerve cord is a

relatively sluggish message-bearer. According to his experiments,

first performed upon the frog, the nervous "current" travels less

than one hundred feet per second. Other experiments performed

soon afterwards by Helmholtz himself, and by various followers,

chief among whom was Du Bois-Reymond, modified somewhat the exact

figures at first obtained, but did not change the general

bearings of the early results. Thus the nervous impulse was shown

to be something far different, as regards speed of transit, at

any rate, from the electric current to which it had been so often

likened. An electric current would flash halfway round the globe

while a nervous impulse could travel the length of the human

body--from a man's foot to his brain.

The tendency to bridge the gulf that hitherto had separated the

physical from the psychical world was further evidenced in the

following decade by Helmholtz's remarkable but highly technical

study of the sensations of sound and of color in connection with

their physical causes, in the course of which he revived the

doctrine of color vision which that other great physiologist and

physicist, Thomas Young, had advanced half a century before. The

same tendency was further evidenced by the appearance, in 1852,

of Dr. Hermann Lotze's famous Medizinische Psychologie, oder

Physiologie der Seele, with its challenge of the old myth of a

"vital force." But the most definite expression of the new

movement was signalized in 1860, when Gustav Fechner published

his classical work called Psychophysik. That title introduced a

new word into the vocabulary of science. Fechner explained it by

saying, "I mean by psychophysics an exact theory of the relation

between spirit and body, and, in a general way, between the

physical and the psychic worlds." The title became famous and the

brunt of many a controversy. So also did another phrase which

Fechner introduced in the course of his book--the phrase

"physiological psychology." In making that happy collocation of

words Fechner virtually christened a new science.


The chief purport of this classical book of the German

psycho-physiologist was the elaboration and explication of

experiments based on a method introduced more than twenty years

earlier by his countryman E. H. Weber, but which hitherto had

failed to attract the attention it deserved. The method consisted

of the measurement and analysis of the definite relation existing

between external stimuli of varying degrees of intensity (various

sounds, for example) and the mental states they induce. Weber's

experiments grew out of the familiar observation that the nicety

of our discriminations of various sounds, weights, or visual

images depends upon the magnitude of each particular cause of a

sensation in its relation with other similar causes. Thus, for

example, we cannot see the stars in the daytime, though they

shine as brightly then as at night. Again, we seldom notice the

ticking of a clock in the daytime, though it may become almost

painfully audible in the silence of the night. Yet again, the

difference between an ounce weight and a two-ounce weight is

clearly enough appreciable when we lift the two, but one cannot

discriminate in the same way between a five-pound weight and a

weight of one ounce over five pounds.

This last example, and similar ones for the other senses, gave

Weber the clew to his novel experiments. Reflection upon

every-day experiences made it clear to him that whenever we

consider two visual sensations, or two auditory sensations, or

two sensations of weight, in comparison one with another, there

is always a limit to the keenness of our discrimination, and that

this degree of keenness varies, as in the case of the weights

just cited, with the magnitude of the exciting cause.

Weber determined to see whether these common experiences could be

brought within the pale of a general law. His method consisted of

making long series of experiments aimed at the determination, in

each case, of what came to be spoken of as the least observable

difference between the stimuli. Thus if one holds an ounce weight

in each hand, and has tiny weights added to one of them, grain by

grain, one does not at first perceive a difference; but

presently, on the addition of a certain grain, he does become

aware of the difference. Noting now how many grains have been

added to produce this effect, we have the weight which represents

the least appreciable difference when the standard is one ounce.

Now repeat the experiment, but let the weights be each of five

pounds. Clearly in this case we shall be obliged to add not

grains, but drachms, before a difference between the two heavy

weights is perceived. But whatever the exact amount added, that

amount represents the stimulus producing a just-perceivable

sensation of difference when the standard is five pounds. And so

on for indefinite series of weights of varying magnitudes. Now

came Weber's curious discovery. Not only did he find that in

repeated experiments with the same pair of weights the measure of

"just-{p}erceivable difference" remained approximately fixed, but

he found, further, that a remarkable fixed relation exists

between the stimuli of different magnitude. If, for example, he

had found it necessary, in the case of the ounce weights, to add

one-fiftieth of an ounce to the one before a difference was

detected, he found also, in the case of the five-pound weights,

that one-fiftieth of five pounds must be added before producing

the same result. And so of all other weights; the amount added

to produce the stimulus of "least-appreciable difference" always

bore the same mathematical relation to the magnitude of the

weight used, be that magnitude great or small.

Weber found that the same thing holds good for the stimuli of the

sensations of sight and of hearing, the differential stimulus

bearing always a fixed ratio to the total magnitude of the

stimuli. Here, then, was the law he had sought.

Weber's results were definite enough and striking enough, yet

they failed to attract any considerable measure of attention

until they were revived and extended by Fechner and brought

before the world in the famous work on psycho-physics. Then they

precipitated a veritable melee. Fechner had not alone verified

the earlier results (with certain limitations not essential to

the present consideration), but had invented new methods of

making similar tests, and had reduced the whole question to

mathematical treatment. He pronounced Weber's discovery the

fundamental law of psycho-physics. In honor of the discoverer, he

christened it Weber's Law. He clothed the law in words and in

mathematical formulae, and, so to say, launched it full tilt at

the heads of the psychological world. It made a fine commotion,

be assured, for it was the first widely heralded bulletin of the

new psychology in its march upon the strongholds of the

time-honored metaphysics. The accomplishments of the

microscopists and the nerve physiologists had been but

preliminary--mere border skirmishes of uncertain import. But here

was proof that the iconoclastic movement meant to invade the very

heart of the sacred territory of mind--a territory from which

tangible objective fact had been supposed to be forever barred.


Hardly had the alarm been sounded, however, before a new movement

was made. While Fechner's book was fresh from the press, steps

were being taken to extend the methods of the physicist in yet

another way to the intimate processes of the mind. As Helmholtz

had shown the rate of nervous impulsion along the nerve tract to

be measurable, it was now sought to measure also the time

required for the central nervous mechanism to perform its work of

receiving a message and sending out a response. This was coming

down to the very threshold of mind. The attempt was first made by

Professor Donders in 1861, but definitive results were only

obtained after many years of experiment on the part of a host of

observers. The chief of these, and the man who has stood in the

forefront of the new movement and has been its recognized leader

throughout the remainder of the century, is Dr. Wilhelm Wundt, of


The task was not easy, but, in the long run, it was accomplished.

Not alone was it shown that the nerve centre requires a

measurable time for its operations, but much was learned as to

conditions that modify this time. Thus it was found that

different persons vary in the rate of their central nervous

activity--which explained the "personal equation" that the

astronomer Bessel had noted a half-century before. It was found,

too, that the rate of activity varies also for the same person

under different conditions, becoming retarded, for example, under

influence of fatigue, or in case of certain diseases of the

brain. All details aside, the essential fact emerges, as an

experimental demonstration, that the intellectual

processes--sensation, apperception, volition--are linked

irrevocably with the activities of the central nervous tissues,

and that these activities, like all other physical processes,

have a time element. To that old school of psychologists, who

scarcely cared more for the human head than for the heels--being

interested only in the mind--such a linking of mind and body as

was thus demonstrated was naturally disquieting. But whatever the

inferences, there was no escaping the facts.

Of course this new movement has not been confined to Germany.

Indeed, it had long had exponents elsewhere. Thus in England, a

full century earlier, Dr. Hartley had championed the theory of

the close and indissoluble dependence of the mind upon the brain,

and formulated a famous vibration theory of association that

still merits careful consideration. Then, too, in France, at the

beginning of the century, there was Dr. Cabanis with his

tangible, if crudely phrased, doctrine that the brain digests

impressions and secretes thought as the stomach digests food and

the liver secretes bile. Moreover, Herbert Spencer's Principles

of Psychology, with its avowed co-ordination of mind and body and

its vitalizing theory of evolution, appeared in 1855, half a

decade before the work of Fechner. But these influences, though

of vast educational value, were theoretical rather than

demonstrative, and the fact remains that the experimental work

which first attempted to gauge mental operations by physical

principles was mainly done in Germany. Wundt's Physiological

Psychology, with its full preliminary descriptions of the anatomy

of the nervous system, gave tangible expression to the growth of

the new movement in 1874; and four years later, with the opening

of his laboratory of physiological psychology at the University

of Leipzig, the new psychology may be said to have gained a

permanent foothold and to have forced itself into official

recognition. From then on its conquest of the world was but a

matter of time.

It should be noted, however, that there is one other method of

strictly experimental examination of the mental field, latterly

much in vogue, which had a different origin. This is the

scientific investigation of the phenomena of hypnotism. This

subject was rescued from the hands of charlatans, rechristened,

and subjected to accurate investigation by Dr. James Braid, of

Manchester, as early as 1841. But his results, after attracting

momentary attention, fell from view, and, despite desultory

efforts, the subject was not again accorded a general hearing

from the scientific world until 1878, when Dr. Charcot took it up

at the Salpetriere, in Paris, followed soon afterwards by Dr.

Rudolf Heidenhain, of Breslau, and a host of other experimenters.

The value of the method in the study of mental states was soon

apparent. Most of Braid's experiments were repeated, and in the

main his results were confirmed. His explanation of hypnotism,

or artificial somnambulism, as a self-induced state, independent

of any occult or supersensible influence, soon gained general

credence. His belief that the initial stages are due to fatigue

of nervous centres, usually from excessive stimulation, has not

been supplanted, though supplemented by notions growing out of

the new knowledge as to subconscious mentality in general, and

the inhibitory influence of one centre over another in the

central nervous mechanism.


These studies of the psychologists and pathologists bring the

relations of mind and body into sharp relief. But even more

definite in this regard was the work of the brain physiologists.

Chief of these, during the middle period of the century, was the

man who is sometimes spoken of as the "father of brain

physiology," Marie Jean Pierre Flourens, of the Jardin des

Plantes of Paris, the pupil and worthy successor of Magendie.

His experiments in nerve physiology were begun in the first

quarter of the century, but his local experiments upon the brain

itself were not culminated until about 1842. At this time the old

dispute over phrenology had broken out afresh, and the studies of

Flourens were aimed, in part at least, at the strictly scientific

investigation of this troublesome topic.

In the course of these studies Flourens discovered that in the

medulla oblongata, the part of the brain which connects that

organ with the spinal cord, there is a centre of minute size

which cannot be injured in the least without causing the instant

death of the animal operated upon. It may be added that it is

this spot which is reached by the needle of the garroter in

Spanish executions, and that the same centre also is destroyed

when a criminal is "successfully" hanged, this time by the forced

intrusion of a process of the second cervical vertebra. Flourens

named this spot the "vital knot." Its extreme importance, as is

now understood, is due to the fact that it is the centre of

nerves that supply the heart; but this simple explanation,

annulling the conception of a specific "life centre," was not at

once apparent.

Other experiments of Flourens seemed to show that the cerebellum

is the seat of the centres that co-ordinate muscular activities,

and that the higher intellectual faculties are relegated to the

cerebrum. But beyond this, as regards localization, experiment

faltered. Negative results, as regards specific faculties, were

obtained from all localized irritations of the cerebrum, and

Flourens was forced to conclude that the cerebral lobe, while

being undoubtedly the seat of higher intellection, performs its

functions with its entire structure. This conclusion, which

incidentally gave a quietus to phrenology, was accepted

generally, and became the stock doctrine of cerebral physiology

for a generation.

It will be seen, however, that these studies of Flourens had a

double bearing. They denied localization of cerebral functions,

but they demonstrated the localization of certain nervous

processes in other portions of the brain. On the whole, then,

they spoke positively for the principle of localization of

function in the brain, for which a certain number of students

contended; while their evidence against cerebral localization was

only negative. There was here and there an observer who felt that

this negative testimony was not conclusive. In particular, the

German anatomist Meynert, who had studied the disposition of

nerve tracts in the cerebrum, was led to believe that the

anterior portions of the cerebrum must have motor functions in

preponderance; the posterior positions, sensory functions.

Somewhat similar conclusions were reached also by Dr.

Hughlings-Jackson, in England, from his studies of epilepsy. But

no positive evidence was forthcoming until 1861, when Dr. Paul

Broca brought before the Academy of Medicine in Paris a case of

brain lesion which he regarded as having most important bearings

on the question of cerebral localization.

The case was that of a patient at the Bicetre, who for twenty

years had been deprived of the power of speech, seemingly through

loss of memory of words. In 1861 this patient died, and an

autopsy revealed that a certain convolution of the left frontal

lobe of his cerebrum had been totally destroyed by disease, the

remainder of his brain being intact. Broca felt that this

observation pointed strongly to a localization of the memory of

words in a definite area of the brain. Moreover, it transpired

that the case was not without precedent. As long ago as 1825 Dr.

Boillard had been led, through pathological studies, to locate

definitely a centre for the articulation of words in the frontal

lobe, and here and there other observers had made tentatives in

the same direction. Boillard had even followed the matter up with

pertinacity, but the world was not ready to listen to him. Now,

however, in the half-decade that followed Broca's announcements,

interest rose to fever-beat, and through the efforts of Broca,

Boillard, and numerous others it was proved that a veritable

centre having a strange domination over the memory of articulate

words has its seat in the third convolution of the frontal lobe

of the cerebrum, usually in the left hemisphere. That part of the

brain has since been known to the English-speaking world as the

convolution of Broca, a name which, strangely enough, the

discoverer's compatriots have been slow to accept.

This discovery very naturally reopened the entire subject of

brain localization. It was but a short step to the inference

that there must be other definite centres worth the seeking, and

various observers set about searching for them. In 1867 a clew

was gained by Eckhard, who, repeating a forgotten experiment by

Haller and Zinn of the previous century, removed portions of the

brain cortex of animals, with the result of producing

convulsions. But the really vital departure was made in 1870 by

the German investigators Fritsch and Hitzig, who, by stimulating

definite areas of the cortex of animals with a galvanic current,

produced contraction of definite sets of muscles of the opposite

side of the body. These most important experiments, received at

first with incredulity, were repeated and extended in 1873 by Dr.

David Ferrier, of London, and soon afterwards by a small army of

independent workers everywhere, prominent among whom were Franck

and Pitres in France, Munck and Goltz in Germany, and Horsley and

Schafer in England. The detailed results, naturally enough, were

not at first all in harmony. Some observers, as Goltz, even

denied the validity of the conclusions in toto. But a consensus

of opinion, based on multitudes of experiments, soon placed the

broad general facts for which Fritsch and Hitzig contended beyond

controversy. It was found, indeed, that the cerebral centres of

motor activities have not quite the finality at first ascribed to

them by some observers, since it may often happen that after the

destruction of a centre, with attending loss of function, there

may be a gradual restoration of the lost function, proving that

other centres have acquired the capacity to take the place of the

one destroyed. There are limits to this capacity for

substitution, however, and with this qualification the

definiteness of the localization of motor functions in the

cerebral cortex has become an accepted part of brain physiology.

Nor is such localization confined to motor centres. Later

experiments, particularly of Ferrier and of Munck, proved that

the centres of vision are equally restricted in their location,

this time in the posterior lobes of the brain, and that hearing

has likewise its local habitation. Indeed, there is every reason

to believe that each form of primary sensation is based on

impressions which mainly come to a definitely localized goal in

the brain. But all this, be it understood, has no reference to

the higher forms of intellection. All experiment has proved

futile to localize these functions, except indeed to the extent

of corroborating the familiar fact of their dependence upon the

brain, and, somewhat problematically, upon the anterior lobes of

the cerebrum in particular. But this is precisely what should be

expected, for the clearer insight into the nature of mental

processes makes it plain that in the main these alleged

"faculties" are not in themselves localized. Thus, for example,

the "faculty" of language is associated irrevocably with centres

of vision, of hearing, and of muscular activity, to go no

further, and only becomes possible through the association of

these widely separated centres. The destruction of Broca's

centre, as was early discovered, does not altogether deprive a

patient of his knowledge of language. He may be totally unable to

speak (though as to this there are all degrees of variation), and

yet may comprehend what is said to him, and be able to read,

think, and even write correctly. Thus it appears that Broca's

centre is peculiarly bound up with the capacity for articulate

speech, but is far enough from being the seat of the faculty of

language in its entirety.

In a similar way, most of the supposed isolated "faculties" of

higher intellection appear, upon clearer analysis, as complex

aggregations of primary sensations, and hence necessarily

dependent upon numerous and scattered centres. Some "faculties,"

as memory and volition, may be said in a sense to be primordial

endowments of every nerve cell--even of every body cell. Indeed,

an ultimate analysis relegates all intellection, in its

primordial adumbrations, to every particle of living matter. But

such refinements of analysis, after all, cannot hide the fact

that certain forms of higher intellection involve a pretty

definite collocation and elaboration of special sensations. Such

specialization, indeed, seems a necessary accompaniment of mental

evolution. That every such specialized function has its

localized centres of co-ordination, of some such significance as

the demonstrated centres of articulate speech, can hardly be in

doubt--though this, be it understood, is an induction, not as yet

a demonstration. In other words, there is every reason to

believe that numerous "centres," in this restricted sense, exist

in the brain that have as yet eluded the investigator. Indeed,

the current conception regards the entire cerebral cortex as

chiefly composed of centres of ultimate co-ordination of

impressions, which in their cruder form are received by more

primitive nervous tissues--the basal ganglia, the cerebellum and

medulla, and the spinal cord.

This, of course, is equivalent to postulating the cerebral cortex

as the exclusive seat of higher intellection. This proposition,

however, to which a safe induction seems to lead, is far afield

from the substantiation of the old conception of brain

localization, which was based on faulty psychology and equally

faulty inductions from few premises. The details of Gall's

system, as propounded by generations of his mostly unworthy

followers, lie quite beyond the pale of scientific discussion.

Yet, as I have said, a germ of truth was there--the idea of

specialization of cerebral functions--and modern investigators

have rescued that central conception from the phrenological

rubbish heap in which its discoverer unfortunately left it



The common ground of all these various lines of investigations of

pathologist, anatomist, physiologist, physicist, and psychologist

is, clearly, the central nervous system--the spinal cord and the

brain. The importance of these structures as the foci of nervous

and mental activities has been recognized more and more with each

new accretion of knowledge, and the efforts to fathom the secrets

of their intimate structure has been unceasing. For the earlier

students, only the crude methods of gross dissections and

microscopical inspection were available. These could reveal

something, but of course the inner secrets were for the keener

insight of the microscopist alone. And even for him the task of

investigation was far from facile, for the central nervous

tissues are the most delicate and fragile, and on many accounts

the most difficult of manipulation of any in the body.

Special methods, therefore, were needed for this essay, and brain

histology has progressed by fitful impulses, each forward jet

marking the introduction of some ingenious improvement of

mechanical technique, which placed a new weapon in the hands of

the investigators.

The very beginning was made in 1824 by Rolando, who first thought

of cutting chemically hardened pieces of brain tissues into thin

sections for microscopical examination--the basal structure upon

which almost all the later advances have been conducted. Muller

presently discovered that bichromate of potassium in solution

makes the best of fluids for the preliminary preservation and

hardening of the tissues. Stilling, in 1842, perfected the

method by introducing the custom of cutting a series of

consecutive sections of the same tissue, in order to trace nerve

tracts and establish spacial relations. Then from time to time

mechanical ingenuity added fresh details of improvement. It was

found that pieces of hardened tissue of extreme delicacy can be

made better subject to manipulation by being impregnated with

collodion or celloidine and embedded in paraffine. Latterly it

has become usual to cut sections also from fresh tissues,

unchanged by chemicals, by freezing them suddenly with vaporized

ether or, better, carbonic acid. By these methods, and with the

aid of perfected microtomes, the worker of recent periods avails

himself of sections of brain tissues of a tenuousness which the

early investigators could not approach.

But more important even than the cutting of thin sections is the

process of making the different parts of the section visible, one

tissue differentiated from another. The thin section, as the

early workers examined it, was practically colorless, and even

the crudest details of its structure were made out with extreme

difficulty. Remak did, indeed, manage to discover that the brain

tissue is cellular, as early as 1833, and Ehrenberg in the same

year saw that it is also fibrillar, but beyond this no great

advance was made until 1858, when a sudden impulse was received

from a new process introduced by Gerlach. The process itself was

most simple, consisting essentially of nothing more than the

treatment of a microscopical section with a solution of carmine.

But the result was wonderful, for when such a section was placed

under the lens it no longer appeared homogeneous. Sprinkled

through its substance were seen irregular bodies that had taken

on a beautiful color, while the matrix in which they were

embedded remained unstained. In a word, the central nerve cell

had sprung suddenly into clear view.

A most interesting body it proved, this nerve cell, or ganglion

cell, as it came to be called. It was seen to be exceedingly

minute in size, requiring high powers of the microscope to make

it visible. It exists in almost infinite numbers, not, however,

scattered at random through the brain and spinal cord. On the

contrary, it is confined to those portions of the central nervous

masses which to the naked eye appear gray in color, being

altogether wanting in the white substance which makes up the

chief mass of the brain. Even in the gray matter, though

sometimes thickly distributed, the ganglion cells are never in

actual contact one with another; they always lie embedded in

intercellular tissues, which came to be known, following Virchow,

as the neuroglia.

Each ganglion cell was seen to be irregular in contour, and to

have jutting out from it two sets of minute fibres, one set

relatively short, indefinitely numerous, and branching in every

direction; the other set limited in number, sometimes even

single, and starting out directly from the cell as if bent on a

longer journey. The numerous filaments came to be known as

protoplasmic processes; the other fibre was named, after its

discoverer, the axis cylinder of Deiters. It was a natural

inference, though not clearly demonstrable in the sections, that

these filamentous processes are the connecting links between the

different nerve cells and also the channels of communication

between nerve cells and the periphery of the body. The white

substance of brain and cord, apparently, is made up of such

connecting fibres, thus bringing the different ganglion cells

everywhere into communication one with another.

In the attempt to trace the connecting nerve tracts through this

white substance by either macroscopical or microscopical methods,

most important aid is given by a method originated by Waller in

1852. Earlier than that, in 1839, Nasse had discovered that a

severed nerve cord degenerates in its peripheral portions. Waller

discovered that every nerve fibre, sensory or motor, has a nerve

cell to or from which it leads, which dominates its nutrition, so

that it can only retain its vitality while its connection with

that cell is intact. Such cells he named trophic centres.

Certain cells of the anterior part of the spinal cord, for

example, are the trophic centres of the spinal motor nerves.

Other trophic centres, governing nerve tracts in the spinal cord

itself, are in the various regions of the brain. It occurred to

Waller that by destroying such centres, or by severing the

connection at various regions between a nervous tract and its

trophic centre, sharply defined tracts could be made to

degenerate, and their location could subsequently be accurately

defined, as the degenerated tissues take on a changed aspect,

both to macroscopical and microscopical observation. Recognition

of this principle thus gave the experimenter a new weapon of

great efficiency in tracing nervous connections. Moreover, the

same principle has wide application in case of the human subject

in disease, such as the lesion of nerve tracts or the destruction

of centres by localized tumors, by embolisms, or by traumatisms.

All these various methods of anatomical examination combine to

make the conclusion almost unavoidable that the central ganglion

cells are the veritable "centres" of nervous activity to which so

many other lines of research have pointed. The conclusion was

strengthened by experiments of the students of motor

localization, which showed that the veritable centres of their

discovery lie, demonstrably, in the gray cortex of the brain, not

in the white matter. But the full proof came from pathology. At

the hands of a multitude of observers it was shown that in

certain well-known diseases of the spinal cord, with resulting

paralysis, it is the ganglion cells themselves that are found to

be destroyed. Similarly, in the case of sufferers from chronic

insanities, with marked dementia, the ganglion cells of the

cortex of the brain are found to have undergone degeneration. The

brains of paretics in particular show such degeneration, in

striking correspondence with their mental decadence. The position

of the ganglion cell as the ultimate centre of nervous activities

was thus placed beyond dispute.

Meantime, general acceptance being given the histological scheme

of Gerlach, according to which the mass of the white substance of

the brain is a mesh-work of intercellular fibrils, a proximal

idea seemed attainable of the way in which the ganglionic

activities are correlated, and, through association, built up, so

to speak, into the higher mental processes. Such a conception

accorded beautifully with the ideas of the associationists, who

had now become dominant in psychology. But one standing puzzle

attended this otherwise satisfactory correlation of anatomical

observations and psychic analyses. It was this: Since, according

to the histologist, the intercellular fibres, along which

impulses are conveyed, connect each brain cell, directly or

indirectly, with every other brain cell in an endless mesh-work,

how is it possible that various sets of cells may at times be

shut off from one another? Such isolation must take place, for

all normal ideation depends for its integrity quite as much upon

the shutting-out of the great mass of associations as upon the

inclusion of certain other associations. For example, a student

in solving a mathematical problem must for the moment become

quite oblivious to the special associations that have to do with

geography, natural history, and the like. But does histology give

any clew to the way in which such isolation may be effected?

Attempts were made to find an answer through consideration of the

very peculiar character of the blood-supply in the brain. Here,

as nowhere else, the terminal twigs of the arteries are arranged

in closed systems, not anastomosing freely with neighboring

systems. Clearly, then, a restricted area of the brain may,

through the controlling influence of the vasomotor nerves, be

flushed with arterial blood while neighboring parts remain

relatively anaemic. And since vital activities unquestionably

depend in part upon the supply of arterial blood, this peculiar

arrangement of the vascular mechanism may very properly be

supposed to aid in the localized activities of the central

nervous ganglia. But this explanation left much to be desired--in

particular when it is recalled that all higher intellection must

in all probability involve multitudes of widely scattered


No better explanation was forthcoming, however, until the year

1889, when of a sudden the mystery was cleared away by a fresh

discovery. Not long before this the Italian histologist Dr.

Camille Golgi had discovered a method of impregnating hardened

brain tissues with a solution of nitrate of silver, with the

result of staining the nerve cells and their processes almost

infinitely better than was possible by the methods of Gerlach, or

by any of the multiform methods that other workers had

introduced. Now for the first time it became possible to trace

the cellular prolongations definitely to their termini, for the

finer fibrils had not been rendered visible by any previous

method of treatment. Golgi himself proved that the set of fibrils

known as protoplasmic prolongations terminate by free

extremities, and have no direct connection with any cell save the

one from which they spring. He showed also that the axis

cylinders give off multitudes of lateral branches not hitherto

suspected. But here he paused, missing the real import of the

discovery of which he was hard on the track. It remained for the

Spanish histologist Dr. S. Ramon y Cajal to follow up the

investigation by means of an improved application of Golgi's

method of staining, and to demonstrate that the axis cylinders,

together with all their collateral branches, though sometimes

extending to a great distance, yet finally terminate, like the

other cell prolongations, in arborescent fibrils having free

extremities. In a word, it was shown that each central nerve

cell, with its fibrillar offshoots, is an isolated entity.

Instead of being in physical connection with a multitude of other

nerve cells, it has no direct physical connection with any other

nerve cell whatever.

When Dr. Cajal announced his discovery, in 1889, his

revolutionary claims not unnaturally amazed the mass of

histologists. There were some few of them, however, who were not

quite unprepared for the revelation; in particular His, who had

half suspected the independence of the cells, because they seemed

to develop from dissociated centres; and Forel, who based a

similar suspicion on the fact that he had never been able

actually to trace a fibre from one cell to another. These

observers then came readily to repeat Cajal's experiments. So

also did the veteran histologist Kolliker, and soon afterwards

all the leaders everywhere. The result was a practically

unanimous confirmation of the Spanish histologist's claims, and

within a few months after his announcements the old theory of

union of nerve cells into an endless mesh-work was completely

discarded, and the theory of isolated nerve elements--the theory

of neurons, as it came to be called--was fully established in its


As to how these isolated nerve cells functionate, Dr. Cajal gave

the clew from the very first, and his explanation has met with

universal approval.

In the modified view, the nerve cell retains its old position as

the storehouse of nervous energy. Each of the filaments jutting

out from the cell is held, as before, to be indeed a transmitter

of impulses, but a transmitter that operates intermittently, like

a telephone wire that is not always "connected," and, like that

wire, the nerve fibril operates by contact and not by continuity.

Under proper stimulation the ends of the fibrils reach out, come

in contact with other end fibrils of other cells, and conduct

their destined impulse. Again they retract, and communication

ceases for the time between those particular cells. Meantime, by

a different arrangement of the various conductors, different sets

of cells are placed in communication, different associations of

nervous impulses induced, different trains of thought engendered.

Each fibril when retracted becomes a non-conductor, but when

extended and in contact with another fibril, or with the body of

another cell, it conducts its message as readily as a continuous

filament could do--precisely as in the case of an electric wire.

This conception, founded on a most tangible anatomical basis,

enables us to answer the question as to how ideas are isolated,

and also, as Dr. Cajal points out, throws new light on many other

mental processes. One can imagine, for example, by keeping in

mind the flexible nerve prolongations, how new trains of thought

may be engendered through novel associations of cells; how

facility of thought or of action in certain directions is

acquired through the habitual making of certain nerve-cell

connections; how certain bits of knowledge may escape our memory

and refuse to be found for a time because of a temporary

incapacity of the nerve cells to make the proper connections, and

so on indefinitely.

If one likens each nerve cell to a central telephone office, each

of its filamentous prolongations to a telephone wire, one can

imagine a striking analogy between the modus operandi of nervous

processes and of the telephone system. The utility of new

connections at the central office, the uselessness of the

mechanism when the connections cannot be made, the "wires in use"

that retard your message, perhaps even the crossing of wires,

bringing you a jangle of sounds far different from what you

desire--all these and a multiplicity of other things that will

suggest themselves to every user of the telephone may be imagined

as being almost ludicrously paralleled in the operations of the

nervous mechanism. And that parallel, startling as it may seem,

is not a mere futile imagining. It is sustained and rendered

plausible by a sound substratum of knowledge of the anatomical

conditions under which the central nervous mechanism exists, and

in default of which, as pathology demonstrates with no less

certitude, its functionings are futile to produce the normal

manifestations of higher intellection.



Conspicuously placed in the great hall of Egyptian antiquities in

the British Museum is a wonderful piece of sculpture known as the

Rosetta Stone. I doubt if any other piece in the entire exhibit

attracts so much attention from the casual visitor as this slab

of black basalt on its telescope-like pedestal. The hall itself,

despite its profusion of strangely sculptured treasures, is never

crowded, but before this stone you may almost always find some

one standing, gazing with more or less of discernment at the

strange characters that are graven neatly across its upturned,

glass-protected face. A glance at this graven surface suffices to

show that three sets of inscriptions are recorded there. The

upper one, occupying about one-fourth of the surface, is a

pictured scroll, made up of chains of those strange outlines of

serpents, hawks, lions, and so on, which are recognized, even by

the least initiated, as hieroglyphics. The middle inscription,

made up of lines, angles, and half-pictures, one might surmise to

be a sort of abbreviated or short-hand hieroglyphic. The third or

lower inscription is Greek--obviously a thing of words. If the

screeds above be also made of words, only the elect have any way

of proving the fact.

Fortunately, however, even the least scholarly observer is left

in no doubt as to the real import of the thing he sees, for an

obliging English label tells us that these three inscriptions are

renderings of the same message, and that this message is a

"decree of the priests of Memphis conferring divine honors on

Ptolemy V. (Epiphenes), King of Egypt, B.C. 195." The label goes

on to state that the upper inscription (of which, unfortunately,

only part of the last dozen lines or so remains, the slab being

broken) is in "the Egyptian language, in hieroglyphics, or

writing of the priests"; the second inscription "in the same

language is in Demotic, or the writing of the people"; and the

third "the Greek language and character." Following this is a

brief biography of the Rosetta Stone itself, as follows: "The

stone was found by the French in 1798 among the ruins of Fort

Saint Julien, near the Rosetta mouth of the Nile. It passed into

the hands of the British by the treaty of Alexandria, and was

deposited in the British Museum in the year 1801." There is a

whole volume of history in that brief inscription--and a bitter

sting thrown in, if the reader chance to be a Frenchman. Yet the

facts involved could scarcely be suggested more modestly. They

are recorded much more bluntly in a graven inscription on the

side of the stone, which reads: "Captured in Egypt by the British

Army, 1801." No Frenchman could read those words without a

veritable sinking of the heart.

The value of the Rosetta Stone depended on the fact that it gave

promise, even when casually inspected, of furnishing a key to the

centuries-old mystery of the hieroglyphics. For two thousand

years the secret of these strange markings had been forgotten.

Nowhere in the world--quite as little in Egypt as elsewhere--had

any man the slightest clew to their meaning; there were those who

even doubted whether these droll picturings really had any

specific meaning, questioning whether they were not rather vague

symbols of esoteric religious import and nothing more. And it was

the Rosetta Stone that gave the answer to these doubters and

restored to the world a lost language and a forgotten literature.

The trustees of the museum recognized at once that the problem of

the Rosetta Stone was one on which the scientists of the world

might well exhaust their ingenuity, and promptly published to the

world a carefully lithographed copy of the entire inscription, so

that foreign scholarship had equal opportunity with the British

to try at the riddle. It was an Englishman, however, who first

gained a clew to the solution. This was none other than the

extraordinary Dr. Thomas Young, the demonstrator of the vibratory

nature of light.

Young's specific discoveries were these: (1) That many of the

pictures of the hieroglyphics stand for the names of the objects

actually delineated; (2) that other pictures are sometimes only

symbolic; (3) that plural numbers are represented by repetition;

(4) that numerals are represented by dashes; (5) that

hieroglyphics may read either from the right or from the left,

but always from the direction in which the animal and human

figures face; (6) that proper names are surrounded by a graven

oval ring, making what he called a cartouche; (7) that the

cartouches of the preserved portion of the Rosetta Stone stand

for the name of Ptolemy alone; (8) that the presence of a female

figure after such cartouches in other inscriptions always denotes

the female sex; (9) that within the cartouches the hieroglyphic

symbols have a positively phonetic value, either alphabetic or

syllabic; and (10) that several different characters may have the

same phonetic value.

Just what these phonetic values are Young pointed out in the case

of fourteen characters representing nine sounds, six of which are

accepted to-day as correctly representing the letters to which he

ascribed them, and the three others as being correct regarding

their essential or consonant element. It is clear, therefore,

that he was on the right track thus far, and on the very verge of

complete discovery. But, unfortunately, he failed to take the

next step, which would have been to realize that the same

phonetic values which were given to the alphabetic characters

within the cartouches were often ascribed to them also when used

in the general text of an inscription; in other words, that the

use of an alphabet was not confined to proper names. This was the

great secret which Young missed and which his French successor,

Jean Francois Champollion, working on the foundation that Young

had laid, was enabled to ferret out.

Young's initial studies of the Rosetta Stone were made in 1814;

his later publication bore date of 1819. Champollion's first

announcement of results came in 1822; his second and more

important one in 1824. By this time, through study of the

cartouches of other inscriptions, Champollion had made out almost

the complete alphabet, and the "riddle of the Sphinx" was

practically solved. He proved that the Egyptians had developed a

relatively complete alphabet (mostly neglecting the vowels, as

early Semitic alphabets did also) centuries before the

Phoenicians were heard of in history. What relation this alphabet

bore to the Phoenician we shall have occasion to ask in another

connection; for the moment it suffices to know that those strange

pictures of the Egyptian scroll are really letters.

Even this statement, however, must be in a measure modified.

These pictures are letters and something more. Some of them are

purely alphabetical in character and some are symbolic in another

way. Some characters represent syllables. Others stand sometimes

as mere representatives of sounds, and again, in a more extended

sense, as representations of things, such as all hieroglyphics

doubtless were in the beginning. In a word, this is an alphabet,

but not a perfected alphabet, such as modern nations are

accustomed to; hence the enormous complications and difficulties

it presented to the early investigators.

Champollion did not live to clear up all these mysteries. His

work was taken up and extended by his pupil Rossellini, and in

particular by Dr. Richard Lepsius in Germany, followed by M.

Bernouf, and by Samuel Birch of the British Museum, and more

recently by such well-known Egyptologists as MM. Maspero and

Mariette and Chabas, in France, Dr. Brugsch, in Germany, and Dr.

E. Wallis Budge, the present head of the Department of Oriental

Antiquities at the British Museum. But the task of later

investigators has been largely one of exhumation and translation

of records rather than of finding methods.


The most casual wanderer in the British Museum can hardly fail to

notice two pairs of massive sculptures, in the one case winged

bulls, in the other winged lions, both human-headed, which guard

the entrance to the Egyptian hall, close to the Rosetta Stone.

Each pair of these weird creatures once guarded an entrance to

the palace of a king in the famous city of Nineveh. As one

stands before them his mind is carried back over some

twenty-seven intervening centuries, to the days when the "Cedar

of Lebanon" was "fair in his greatness" and the scourge of


The very Sculptures before us, for example, were perhaps seen by

Jonah when he made that famous voyage to Nineveh some seven or

eight hundred years B.C. A little later the Babylonian and the

Mede revolted against Assyrian tyranny and descended upon the

fair city of Nineveh, and almost literally levelled it to the

ground. But these great sculptures, among other things, escaped

destruction, and at once hidden and preserved by the accumulating

debris of the centuries, they stood there age after age, their

very existence quite forgotten. When Xenophon marched past their

site with the ill-starred expedition of the ten thousand, in the

year 400 B.C., he saw only a mound which seemed to mark the site

of some ancient ruin; but the Greek did not suspect that he

looked upon the site of that city which only two centuries before

had been the mistress of the world.

So ephemeral is fame! And yet the moral scarcely holds in the

sequel; for we of to-day, in this new, undreamed-of Western

world, behold these mementos of Assyrian greatness fresh from

their twenty-five hundred years of entombment, and with them

records which restore to us the history of that long-forgotten

people in such detail as it was not known to any previous

generation since the fall of Nineveh. For two thousand five

hundred years no one saw these treasures or knew that they

existed. One hundred generations of men came and went without

once pronouncing the name of kings Shalmaneser or Asumazirpal or

Asurbanipal. And to-day, after these centuries of oblivion,

these names are restored to history, and, thanks to the character

of their monuments, are assured a permanency of fame that can

almost defy time itself. It would be nothing strange, but rather

in keeping with their previous mutations of fortune, if the names

of Asurnazirpal and Asurbanipal should be familiar as household

words to future generations that have forgotten the existence of

an Alexander, a Caesar, and a Napoleon. For when Macaulay's

prospective New Zealander explores the ruins of the British

Museum the records of the ancient Assyrians will presumably still

be there unscathed, to tell their story as they have told it to

our generation, though every manuscript and printed book may have

gone the way of fragile textures.

But the past of the Assyrian sculptures is quite necromantic

enough without conjuring for them a necromantic future. The story

of their restoration is like a brilliant romance of history.

Prior to the middle of this century the inquiring student could

learn in an hour or so all that was known in fact and in fable of

the renowned city of Nineveh. He had but to read a few chapters

of the Bible and a few pages of Diodorus to exhaust the important

literature on the subject. If he turned also to the pages of

Herodotus and Xenophon, of Justin and Aelian, these served

chiefly to confirm the suspicion that the Greeks themselves knew

almost nothing more of the history of their famed Oriental

forerunners. The current fables told of a first King Ninus and

his wonderful queen Semiramis; of Sennacherib the conqueror; of

the effeminate Sardanapalus, who neglected the warlike ways of

his ancestors but perished gloriously at the last, with Nineveh

itself, in a self-imposed holocaust. And that was all. How much

of this was history, how much myth, no man could say; and for all

any one suspected to the contrary, no man could ever know. And

to-day the contemporary records of the city are before us in such

profusion as no other nation of antiquity, save Egypt alone, can

at all rival. Whole libraries of Assyrian books are at hand that

were written in the seventh century before our era. These, be it

understood, are the original books themselves, not copies. The

author of that remote time appeals to us directly, hand to eye,

without intermediary transcriber. And there is not a line of any

Hebrew or Greek manuscript of a like age that has been preserved

to us; there is little enough that can match these ancient books

by a thousand years. When one reads Moses or Isaiah, Homer,

Hesiod, or Herodotus, he is but following the

transcription--often unquestionably faulty and probably never in

all parts perfect--of successive copyists of later generations.

The oldest known copy of the Bible, for example, dates probably

from the fourth century A.D., a thousand years or more after the

last Assyrian records were made and read and buried and


There was at least one king of Assyria--namely, Asurbanipal,

whose palace boasted a library of some ten thousand volumes--a

library, if you please, in which the books were numbered and

shelved systematically, and classified and cared for by an

official librarian. If you would see some of the documents of

this marvellous library you have but to step past the winged

lions of Asurnazirpal and enter the Assyrian hall just around the

corner from the Rosetta Stone. Indeed, the great slabs of stone

from which the lions themselves are carved are in a sense books,

inasmuch as there are written records inscribed on their surface.

A glance reveals the strange characters in which these records

are written, graven neatly in straight lines across the stone,

and looking to casual inspection like nothing so much as random

flights of arrow-heads. The resemblance is so striking that this

is sometimes called the arrow-head character, though it is more

generally known as the wedge or cuneiform character. The

inscriptions on the flanks of the lions are, however, only

makeshift books. But the veritable books are no farther away

than the next room beyond the hall of Asurnazirpal. They occupy

part of a series of cases placed down the centre of this room.

Perhaps it is not too much to speak of this collection as the

most extraordinary set of documents of all the rare treasures of

the British Museum, for it includes not books alone, but public

and private letters, business announcements, marriage

contracts--in a word, all the species of written records that

enter into the every-day life of an intelligent and cultured


But by what miracle have such documents been preserved through

all these centuries? A glance makes the secret evident. It is

simply a case of time-defying materials. Each one of these

Assyrian documents appears to be, and in reality is, nothing more

or less than an inscribed fragment of brick, having much the

color and texture of a weathered terra-cotta tile of modern

manufacture. These slabs are usually oval or oblong in shape,

and from two or three to six or eight inches in length and an

inch or so in thickness. Each of them was originally a portion

of brick-clay, on which the scribe indented the flights of

arrowheads with some sharp-cornered instrument, after which the

document was made permanent by baking. They are somewhat fragile,

of course, as all bricks are, and many of them have been more or

less crumbled in the destruction of the palace at Nineveh; but to

the ravages of mere time they are as nearly invulnerable as

almost anything in nature. Hence it is that these records of a

remote civilization have been preserved to us, while the similar

records of such later civilizations as the Grecian have utterly

perished, much as the flint implements of the cave-dweller come

to us unchanged, while the iron implements of a far more recent

age have crumbled away.


After all, then, granted the choice of materials, there is

nothing so very extraordinary in the mere fact of preservation of

these ancient records. To be sure, it is vastly to the credit of

nineteenth-century enterprise to have searched them out and

brought them back to light. But the real marvel in connection

with them is the fact that nineteenth-century scholarship should

have given us, not the material documents themselves, but a

knowledge of their actual contents. The flight of arrow-heads on

wall or slab or tiny brick have surely a meaning; but how shall

we guess that meaning? These must be words; but what words? The

hieroglyphics of the Egyptians were mysterious enough in all

conscience; yet, after all, their symbols have a certain

suggestiveness, whereas there is nothing that seems to promise a

mental leverage in the unbroken succession of these cuneiform

dashes. Yet the Assyrian scholar of to-day can interpret these

strange records almost as readily and as surely as the classical

scholar interprets a Greek manuscript. And this evidences one of

the greatest triumphs of nineteenth-century scholarship, for

within almost two thousand years no man has lived, prior to our

century, to whom these strange inscriptions would not have been

as meaningless as they are to the most casual stroller who looks

on them with vague wonderment here in the museum to-day. For the

Assyrian language, like the Egyptian, was veritably a dead

language; not, like Greek and Latin, merely passed from practical

every-day use to the closet of the scholar, but utterly and

absolutely forgotten by all the world. Such being the case, it is

nothing less than marvellous that it should have been restored.

It is but fair to add that this restoration probably never would

have been effected, with Assyrian or with Egyptian, had the

language in dying left no cognate successor; for the powers of

modern linguistry, though great, are not actually miraculous.

But, fortunately, a language once developed is not blotted out in

toto; it merely outlives its usefulness and is gradually

supplanted, its successor retaining many traces of its origin.

So, just as Latin, for example, has its living representatives in

Italian and the other Romance tongues, the language of Assyria is

represented by cognate Semitic languages. As it chances, however,

these have been of aid rather in the later stages of Assyrian

study than at the very outset; and the first clew to the message

of the cuneiform writing came through a slightly different


Curiously enough, it was a trilingual inscription that gave the

clew, as in the case of the Rosetta Stone, though with very

striking difference withal. The trilingual inscription now in

question, instead of being a small, portable monument, covers the

surface of a massive bluff at Behistun in western Persia.

Moreover, all three of its inscriptions are in cuneiform

characters, and all three are in languages that at the beginning

of our century were absolutely unknown. This inscription itself,

as a striking monument of unknown import, had been seen by

successive generations. Tradition ascribed it, as we learn from

Ctesias, through Diodorus, to the fabled Assyrian queen

Semiramis. Tradition was quite at fault in this; but it is only

recently that knowledge has availed to set it right. The

inscription, as is now known, was really written about the year

515 B.C., at the instance of Darius I., King of Persia, some of

whose deeds it recounts in the three chief languages of his

widely scattered subjects.

The man who at actual risk of life and limb copied this wonderful

inscription, and through interpreting it became the veritable

"father of Assyriology," was the English general Sir Henry

Rawlinson. His feat was another British triumph over the same

rivals who had competed for the Rosetta Stone; for some French

explorers had been sent by their government, some years earlier,

expressly to copy this strange record, and had reported that it

was impossible to reach the inscription. But British courage did

not find it so, and in 1835 Rawlinson scaled the dangerous height

and made a paper cast of about half the inscription. Diplomatic

duties called him away from the task for some years, but in 1848

he returned to it and completed the copy of all parts of the

inscription that have escaped the ravages of time. And now the

material was in hand for a new science, which General Rawlinson

himself soon, assisted by a host of others, proceeded to


The key to the value of this unique inscription lies in the fact

that its third language is ancient Persian. It appears that the

ancient Persians had adopted the cuneiform character from their

western neighbors, the Assyrians, but in so doing had made one of

those essential modifications and improvements which are scarcely

possible to accomplish except in the transition from one race to

another. Instead of building with the arrow-head a multitude of

syllabic characters, including many homophones, as had been and

continued to be the custom with the Assyrians, the Persians

selected a few of these characters and ascribed to them phonetic

values that were almost purely alphabetic. In a word, while

retaining the wedge as the basal stroke of their script, they

developed an alphabet, making the last wonderful analysis of

phonetic sounds which even to this day has escaped the Chinese,

which the Egyptians had only partially effected, and which the

Phoenicians were accredited by the Greeks with having introduced

to the Western world. In addition to this all-essential step, the

Persians had introduced the minor but highly convenient custom of

separating the words of a sentence from one another by a

particular mark, differing in this regard not only from the

Assyrians and Egyptians, but from the early Greek scribes as


Thanks to these simplifications, the old Persian language had

been practically restored about the beginning of the nineteenth

century, through the efforts of the German Grotefend, and further

advances in it were made just at this time by Renouf, in France,

and by Lassen, in Germany, as well as by Rawlinson himself, who

largely solved the problem of the Persian alphabet independently.

So the Persian portion of the Behistun inscription could be at

least partially deciphered. This in itself, however, would have

been no very great aid towards the restoration of the languages

of the other portions had it not chanced, fortunately, that the

inscription is sprinkled with proper names. Now proper names,

generally speaking, are not translated from one language to

another, but transliterated as nearly as the genius of the

language will permit. It was the fact that the Greek word

Ptolemaics was transliterated on the Rosetta Stone that gave the

first clew to the sounds of the Egyptian characters. Had the

upper part of the Rosetta Stone been preserved, on which,

originally, there were several other names, Young would not have

halted where he did in his decipherment.

But fortune, which had been at once so kind and so tantalizing in

the case of the Rosetta Stone, had dealt more gently with the

Behistun inscriptions; for no fewer than ninety proper names were

preserved in the Persian portion and duplicated, in another

character, in the Assyrian inscription. A study of these gave a

clew to the sounds of the Assyrian characters. The decipherment

of this character, however, even with this aid, proved enormously

difficult, for it was soon evident that here it was no longer a

question of a nearly perfect alphabet of a few characters, but of

a syllabary of several hundred characters, including many

homophones, or different forms for representing the same sound.

But with the Persian translation for a guide on the one hand, and

the Semitic languages, to which family the Assyrian belonged, on

the other, the appalling task was gradually accomplished, the

leading investigators being General Rawlinson, Professor Hincks,

and Mr. Fox-Talbot, in England, Professor Jules Oppert, in Paris,

and Professor Julian Schrader, in Germany, though a host of other

scholars soon entered the field.

This great linguistic feat was accomplished about the middle of

the nineteenth century. But so great a feat was it that many

scholars of the highest standing, including Joseph Erneste Renan,

in France, and Sir G. Cornewall Lewis, in England, declined at

first to accept the results, contending that the Assyriologists

had merely deceived themselves by creating an arbitrary language.

The matter was put to a test in 1855 at the suggestion of Mr.

Fox-Talbot, when four scholars, one being Mr. Talbot himself and

the others General Rawlinson, Professor Hincks, and Professor

Oppert, laid before the Royal Asiatic Society their independent

interpretations of a hitherto untranslated Assyrian text. A

committee of the society, including England's greatest historian

of the century, George Grote, broke the seals of the four

translations, and reported that they found them unequivocally in

accord as regards their main purport, and even surprisingly

uniform as regards the phraseology of certain passages--in short,

as closely similar as translations from the obscure texts of any

difficult language ever are. This decision gave the work of the

Assyriologists official status, and the reliability of their

method has never since been in question. Henceforth Assyriology

was an established science.




[1] Robert Boyle, Philosophical Works (3 vols.). London, 1738.


[1] For a complete account of the controversy called the "Water

Controversy," see The Life of the Hon. Henry Cavendish, by George

Wilson, M.D., F.R.S.E. London, 1850.

[2] Henry Cavendish, in Phil. Trans. for 1784, P. 119.

[3] Lives of the Philosophers of the Time of George III., by

Henry, Lord Brougham, F.R.S., p. 106. London, 1855.

[4] Experiments and Observations on Different Kinds of Air, by

Joseph Priestley (3 vols.). Birmingham, 790, vol. II, pp.


[5] Lectures on Experimental Philosophy, by Joseph Priestley,

lecture IV., pp. 18, ig. J. Johnson, London, 1794.

[6] Translated from Scheele's Om Brunsten, eller Magnesia, och

dess Egenakaper. Stockholm, 1774, and published as Alembic Club

Reprints, No. 13, 1897, p. 6.

[7] According to some writers this was discovered by Berzelius.

[8] Histoire de la Chimie, par Ferdinand Hoefer. Paris, 1869,

Vol. CL, p. 289.

[9] Elements of Chemistry, by Anton Laurent Lavoisier, translated

by Robert Kerr, p. 8. London and Edinburgh, 1790.

[10] Ibid., pp. 414-416.


[1] Sir Humphry Davy, in Phil. Trans., Vol. VIII.


[1] Baas, History of Medicine, p. 692.

[2] Based on Thomas H. Huxley's Presidential Address to the

British Association for the Advancement of Science, 1870.

[3] Essays on Digestion, by James Carson. London, 1834, p. 6.

[4] Ibid., p. 7.

[5] John Hunter, On the Digestion of the Stomach after Death,

first edition, pp. 183-188.

[6] Erasmus Darwin, The Botanic Garden, pp. 448-453. London,



[1] Baron de Cuvier's Theory of the Earth. New York, 1818, p.


[2] On the Organs and Mode of Fecundation of Orchidex and

Asclepiadea, by Robert Brown, Esq., in Miscellaneous Botanical

Works. London, 1866, Vol. I., pp. 511-514.

[3] Justin Liebig, Animal Chemistry. London, 1843, p. 17f.


[1] "Essay on the Metamorphoses of Plants," by Goethe, translated

for the present work from Grundriss einer Geschichte der

Naturwissenschaften, by Friederich Dannemann (2 vols.). Leipzig,

1896, Vol. I., p. 194.

[2] The Temple of Nature, or The Origin of Society, by Erasmus

Darwin, edition published in 1807, p. 35.

[3] Baron de Cuvier, Theory of the Earth. New York, 1818, p.74.

(This was the introduction to Cuvier's great work.)

[4] Robert Chambers, Explanations: a sequel to Vestiges of

Creation. London, Churchill, 1845, pp. 148-153.


[1] Condensed from Dr. Boerhaave's Academical Lectures on the

Theory of Physic. London, 1751, pp. 77, 78. Boerhaave's lectures

were published as Aphorismi de cognoscendis et curandis Morbis,

Leyden, 1709. On this book Van Swieten wrote commentaries filling

five volumes. Another very celebrated work of Boerhaave is his

Institutiones et Experimenta Chemic, Paris, 1724, the germs of

this being given as a lecture on his appointment to the chair of

chemistry in the University of Leyden in 1718.

[2] An Inquiry into the Causes and Effects of the Variola

Vaccine, etc., by Edward Jenner, M.D., F.R.S., etc. London, 1799,

pp. 2-7. He wrote several other papers, most of which were

communications to the Royal Society. His last publication was, On

the Influence of Artificial Eruptions in Certain Diseases

(London, 1822), a subject to which he had given much time and



[1] In the introduction to Corvisart's translation of

Avenbrugger's work. Paris, 1808.

[2] Laennec, Traite d'Auscultation Mediate. Paris, 1819. This was

Laennec's chief work, and was soon translated into several

different languages. Before publishing this he had written also,

Propositions sur la doctrine midicale d'Hippocrate, Paris, 1804,

and Memoires sur les vers visiculaires, in the same year.

[3] Researches, Chemical and Philosophical, chiefly concerning

Nitrous Oxide or Dephlogisticated Nitrous Air and its

Respiration, by Humphry Davy. London, 1800, pp. 479-556.

[4] Ibid.

[5] For accounts of the discovery of anaesthesia, see Report of

the Board of Trustees of the Massachusetts General Hospital,

Boston, 1888. Also, The Ether Controversy: Vindication of the

Hospital Reports of 1848, by N. L Bowditch, Boston, 1848. An

excellent account is given in Littell's Living Age, for March,

1848, written by R. H. Dana, Jr. There are also two Congressional

Reports on the question of the discovery of etherization, one for

1848, the other for 11852.

[6] Simpson made public this discovery of the anaesthetic

properties of chloroform in a paper read before the

Medico-Chirurgical Society of Edinburgh, in March, 1847, about

three months after he had first seen a surgical operation

performed upon a patient to whom ether had been administered.

[7] Louis Pasteur, Studies on Fermentation. London, 1870.

[8] Louis Pasteur, in Comptes Rendus des Sciences de L'Academie

des Sciences, vol. XCII., 1881, pp. 429-435.


[1] Bell's communications were made to the Royal Society, but his

studies and his discoveries in the field of anatomy of the

nervous system were collected and published, in 1824, as An

Exposition of the Natural System of Nerves of the Human Body:

being a Republication of the Papers delivered to the Royal

Society on the Subject of the Nerves.

[2] Marshall Hall, M.D., F.R.S.L., On the Reflex Functions of the

Medulla Oblongata and the Medulla Spinalis, in Phil. Trans. of

Royal Soc., vol. XXXIII., 1833.

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