CHAPTER I. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES

Produced by Charles Keller

A HISTORY OF SCIENCE

By Henry Smith Williams, M.D., LL.D.

Assisted By Edward H. Williams, M.D.

In Five Volumes

Volume IV.

MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES

BOOK IV. MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES

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.

I. THE PHLOGISTON THEORY IN CHEMISTRY

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 heavier.

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.

II. THE BEGINNINGS OF MODERN CHEMISTRY

THE "PNEUMATIC" CHEMISTS

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, he 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 chemistry.

JOSEPH BLACK

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, he 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.

HENRY CAVENDISH

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 Watt.

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

whatever."(2)

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 he came back a second time he found his master had

expired."(3)

JOSEPH PRIESTLEY

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 words:

"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 air.

"... 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)

KARL WILHELM SCHEELE

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 substances.

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

itself.

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.

LAVOISIER AND THE FOUNDATION OF MODERN CHEMISTRY

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 well.

"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 days.

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 vain.

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.

III. CHEMISTRY SINCE THE TIME OF DALTON

JOHN DALTON AND THE ATOMIC THEORY

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

proportions.

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 he 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.

HUMPHRY DAVY AND ELECTRO-CHEMISTRY

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

miraculous.

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 battery.

"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.

ORGANIC CHEMISTRY AND THE IDEA OF THE MOLECULE

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 generation.

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 radicals.

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 disfavor.

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.

CHEMICAL AFFINITY

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 compounds.

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.

PERIODICITY OF ATOMIC WEIGHTS

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.

NEW WEAPONS--SPECTROSCOPE AND CAMERA

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 constitution.

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.

IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY

ALBRECHT VON HALLER

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

unanswered.

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 Darwinism."(1)

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 pulse.

BATTISTA MORGAGNI AND MORBID ANATOMY

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

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.

JOHN HUNTER

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 living."

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 established.

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 route.

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

Hunter's.

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 fellow-physician.

LAZZARO SPALLANZANI

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 he 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.

THE CHEMICAL THEORY OF DIGESTION

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, he 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

continuance."(5)

THE FUNCTION OF RESPIRATION

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.

ERASMUS DARWIN AND VEGETABLE PHYSIOLOGY

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 question:

"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 offices.

"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 observations:

"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

veins."(6)

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.

ZOOLOGY AT THE CLOSE OF THE EIGHTEENTH CENTURY

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.

V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY

CUVIER AND THE CORRELATION OF PARTS

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.

BICHAT AND THE BODILY TISSUES

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 classification.

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.

LISTER AND THE PERFECTED MICROSCOPE

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 one.

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."

ROBERT BROWN AND THE CELL NUCLEUS

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 column.

"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)

SCHLEIDEN AND SCHWANN AND THE CELL THEORY

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.

THE CELL THEORY ELABORATED

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 he 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.

ANIMAL CHEMISTRY

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 acid.

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 stomach.

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:

LIEBIG ON ANIMAL HEAT

"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 oxygen.

"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 medium.

"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 combustion."(3)

BLOOD CORPUSCLES, MUSCLES, AND GLANDS

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 organism?

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 unquestioned.

A consideration of the functions of that other set of organs known

collectively as the nervous system is reserved for a later chapter.

VI. THEORIES OF ORGANIC EVOLUTION

GOETHE AND THE METAMORPHOSIS OF PARTS

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 leaves.

"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 form.

"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 two.

"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.

ERASMUS DARWIN

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 Nature:

"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 implications.

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.

LAMARCK VERSUS CUVIER

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 themselves.

"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 to-day.

"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 prophet.

TENTATIVE ADVANCES

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 concerned.

"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.

DARWIN AND THE ORIGIN OF SPECIES

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 reverberation.

NEW CHAMPIONS

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."

THE ORIGIN OF THE FITTEST

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.

VII. EIGHTEENTH-CENTURY MEDICINE

THE SYSTEM OF BOERHAAVE

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 Actions.

"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 Prophylaxis.

"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."

ANIMISTS, VITALISTS, AND ORGANICISTS

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 itself.

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.

THE SYSTEM OF HAHNEMANN

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.

JENNER AND VACCINATION

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 enough.

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 subject.

"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 distemper."(2)

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.

VIII. NINETEENTH-CENTURY MEDICINE

PHYSICAL DIAGNOSIS

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 selection.

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 physician.

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.

PARASITIC DISEASES

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 repercutee."

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 acceptance.

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.

PAINLESS SURGERY

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.

PASTEUR AND THE GERM THEORY OF DISEASE

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 micro-organisms.

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.

EXPERIMENTS WITH GRAPE SUGAR

"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 facts:

"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."

FOREIGN ORGANISMS AND THE WORT OF BEER

"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 expounding.

"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 germs."(7)

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 anthrax.

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.

LISTER AND ANTISEPTIC SURGERY

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 before.

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 condition.

PREVENTIVE INOCULATION

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 economy.

"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 known.

"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 controversy.

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 Nha-Trang.

SERUM-THERAPY

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 Buda-Pesth.

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 purpose.

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 China.

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 Australia.

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.

IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY

BRAIN AND MIND

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 Spurzheim.

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.

FUNCTIONS OF THE NERVES

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 wire.

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

science.

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 hereafter.

"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 clearly.

"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.

PSYCHO-PHYSICS

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.

FECHNER EXPOUNDS WEBER'S LAW

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.

PHYSIOLOGICAL PSYCHOLOGY

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

Leipzig.

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.

THE BRAIN AS THE ORGAN OF MIND

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 buried.

THE MINUTE STRUCTURE OF THE BRAIN

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 centres.

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

place.

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.

X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY

HOW THE "RIDDLE OF THE SPHINX" WAS READ

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.

TREASURES FROM NINEVEH

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 Israel.

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 forgotten.

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 community.

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.

HOW THE RECORDS WERE READ

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 channel.

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 elaborate.

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 well.

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.

APPENDIX

REFERENCE-LIST

CHAPTER I. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES

(1) Robert Boyle, Philosophical Works (3 vols.). London, 1738.