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A History of Science, Volume 4

Part 4 out of 5

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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

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