PART I

Transcriber's note:

Minor spelling and punctuation inconsistencies been harmonized.

Obvious printer errors have been repaired. Italic text has been

marked with _underscores_. Please see the end of this book for

further notes.

EXPERIMENTS ON ANIMALS

[Illustration: BRAIN OF AN ANTHROPOID APE, SHOWING THE POSITION OF THE

MOTOR CENTRES.

(From a paper by Sir Victor Horsley and Dr. Beevor. _Phil. Trans. Roy.

Soc._, 1892.)]

EXPERIMENTS

ON ANIMALS

BY

STEPHEN PAGET

WITH AN INTRODUCTION BY

LORD LISTER

THIRD AND REVISED EDITION

"_Perhaps it is wrong to compare sin with sin, but I

declare to you, the more I think of it, the more intimately

does this Prejudice seem to me to corrupt the soul, even

beyond those sins which are commonly called more

deadly._"--CARDINAL NEWMAN.

NEW YORK

WILLIAM WOOD AND COMPANY

MDCCCCVII

TO

CHARLES ALFRED BALLANCE

M.S., F.R.C.S.

AND

WILLIAM HUNTER

M.D., F.R.C.P.

PREFACE

The first edition of this book was published in 1900. For twelve years

it had been my business, as Secretary to the Association for the

Advancement of Medicine by Research, to know something about

experiments on animals, and to follow the working of the Act of 1876;

and to give facts and references to a very large number of applicants.

Believing that an account of these experiments, and of the conditions

imposed on them by the Act, might serve a useful purpose, I proposed

to the Council of the Association that I should write a book on the

subject. The Council accepted this proposal; and decided that the book

should be written for general reading, that it should not be

anonymous, and that it should be published without reserve.

It was, of course, a doubtful and embarrassing task. But, from twelve

years' experience of the things said by the chief opponents of all

experiments on animals, I knew that there was only one way of doing

it--to give the original authorities, the plain facts, the very words,

chapter and verse for everything.

Among those who kindly revised the proofs were Prof. Rose Bradford and

Prof. Starling, who revised Part I.; Mr. Shattock, who revised Part

II.; and Prof. Schäfer. Valuable help was given by Mr. R. H. Clarke,

Sir Victor Horsley, Dr. Beevor, Prof. Ronald Ross, and the late Dr.

Washbourn; and I was allowed to make free use of Mr. George Pernet's

careful researches into the history of the subject. Lord Lister

himself did me the honour to read and correct, with the utmost

patience, Parts I. and II.

In the second edition (1904) some mistakes were corrected, and some

facts were added.

The present edition has been thoroughly revised; and I have included

in it a reprint, with some changes and omissions, of a pamphlet, _The

Case against Anti-vivisection_, which I wrote in 1904.

1906.

INTRODUCTION TO THE FIRST EDITION

This work by Mr. Paget is entirely a labour of love. Not being himself

engaged in researches involving experiments upon the lower animals, he

is not directly interested in the subject. But, in his official

capacity as Secretary (1887-1899) to the Association for the

Advancement of Medicine by Research, he has become widely conversant

with such investigations, and has been deeply impressed with the

greatness of the benefits which they have conferred upon mankind, and

the grievous mistake that is made by those who desire to suppress

them.

The action of these well-meaning persons is based upon ignorance. They

allow that man is permitted to inflict pain upon the lower animals

when some substantial advantage is to be gained; but they deny that

any good has ever resulted from the researches which they condemn.

How far such statements are from the truth will be evident to those

who peruse this book. Its earlier pages deal with Physiology, the main

basis of all sound medicine and surgery. The examples given in this

department are not numerous; they are, however, sufficiently striking,

as indications that, from the discovery of the circulation of the

blood onwards, our knowledge of healthy animal function has been

mainly derived from experiments on animals.

The chief bulk of the work is devoted to the class of investigations

which are most frequent at the present day; and it shows what a flood

of light has been already thrown by Bacteriology upon the nature of

human disease and the means of combating it.

The chapter on the Action of Drugs will be to many a startling

disclosure of the gross ignorance that prevailed among physicians even

in the earlier part of last century. The great revolution that has

since taken place is no doubt largely due to advances in sciences

other than Biology, especially Chemistry. But it could not have

attained its present proportions without the ever-increasing knowledge

of Physiology, based on experiments on animals; and Mr. Paget shows

how large a share these have had in the direct investigation of

articles of the Materia Medica.

The concluding part of the volume discusses the restrictions which

have been placed by the legislature in this country on those engaged

in these researches, with the view of obviating possible abuse.

Whether the Act in question has been really useful, whether it has not

done more harm than good, by hampering and sometimes entirely

preventing legitimate and beneficent investigation, I will not now

discuss.

Meanwhile I commend Mr. Paget's book to the careful consideration of

the reader.

LISTER.

CONTENTS

PART I

EXPERIMENTS IN PHYSIOLOGY

PAGE

I. THE BLOOD 3

II. THE LACTEALS 19

III. THE GASTRIC JUICE 24

IV. GLYCOGEN 30

V. THE PANCREAS 36

VI. THE GROWTH OF BONE 40

VII. THE NERVOUS SYSTEM 44

PART II

EXPERIMENTS IN PATHOLOGY, MATERIA

MEDICA, AND THERAPEUTICS

I. INFLAMMATION, SUPPURATION,

AND BLOOD-POISONING 75

II. ANTHRAX 87

III. TUBERCLE 96

IV. DIPHTHERIA 102

V. TETANUS 128

VI. RABIES 137

VII. CHOLERA 152

VIII. PLAGUE 168

IX. TYPHOID FEVER; MALTA FEVER 196

X. THE MOSQUITO: MALARIA,

YELLOW FEVER, FILARIASIS 214

XI. PARASITIC DISEASES 243

XII. MYXOEDEMA 247

XIII. THE ACTION OF DRUGS 251

XIV. SNAKE-VENOM 259

PART III

THE ACT RELATING TO EXPERIMENTS ON ANIMALS

IN GREAT BRITAIN AND IRELAND

I. TEXT OF THE ACT 271

II. ANÆSTHETICS UNDER THE ACT 281

III. INSPECTORS' REPORT, 1905 283

PART IV

THE CASE AGAINST ANTI-VIVISECTION

I. ANTI-VIVISECTION SOCIETIES 297

II. LITERATURE 313

III. ARGUMENTS 325

IV. "OUR CAUSE IN PARLIAMENT" 367

V. A HISTORICAL PARALLEL 371

INDEX 377

PART I

EXPERIMENTS IN PHYSIOLOGY

EXPERIMENTS ON ANIMALS

I

THE BLOOD

I.--BEFORE HARVEY

Galen, born at Pergamos, 131 A.D., proved by experiments on animals

that the brain is as warm as the heart, against the Aristotelian

doctrine that the office of the brain is to keep the heart cool. He

also proved that the arteries during life contain blood, not [Greek:

pneuma], or the breath of life:--

"Ourselves, having tied the exposed arteries above and below,

opened them between the ligatures, and showed that they were

indeed full of blood."

Though all vessels bleed when they are wounded, yet this experiment

was necessary to refute the fanciful teaching of Erasistratus and his

followers, of whom Galen says:--

"Erasistratus is pleased to believe that an artery is a vessel

containing the breath of life, and a vein is a vessel containing

blood; and that the vessels, dividing again and again, come at

last to be so small that they can close their ultimate pores,

and keep the blood controlled within them; yea, though the pores

of the vein and of the artery lie side by side, yet the blood

remains within its proper bounds, nowhere passing into the

vessels of the breath of life. But when the blood is driven with

violence from the veins into the arteries, forthwith there is

disease; and the blood is poured the wrong way into the

arteries, and there withstands and dashes itself against the

breath of life coming from the heart, and turns the course of

it--and this forsooth is fever."

For many centuries after Galen, men were content to worship his name

and his doctrines, and forsook his method. They did not follow the way

of experiment, and invented theories that were no help either in

science or in practice. Here, in Galen's observation of living

arteries, was a great opportunity for physiology; but the example that

he set to those who came after him was forgotten by them, and, from

the time of Galen to the time of the Renaissance, physiology remained

almost where he had left it. Of the men of the Renaissance, Servetus,

Cæsalpinus, Ruinius, and others, Harvey's near predecessors, this much

only need be said here, that they did not discover the circulation of

the blood; and that the claim made a few years ago to this discovery,

on behalf of Cæsalpinus, by his countrymen, was not successful. But it

is probable that Realdus (1516-1557) did understand the passage of

blood through the lungs, but not the general circulation. He says:--

"The blood is carried through the pulmonary artery to the lung,

and there is attenuated; thence, mixed with air, it is carried

through the pulmonary vein to the left ventricle of the heart:

which thing no man hitherto has noted or left on record, though

it is most worthy of the observation of all men.... And this is

as true as truth itself; for if you will look, not only in the

dead body but also in the living animal, you will always find

this pulmonary vein full of blood, which assuredly it would not

be if it were designed only for air and vapours.... Verily, I

pray you, O candid reader, studious of authority, but more

studious of truth, to make experiment on animals. You will find

the pulmonary vein full of blood, not air or _fuligo_, as these

men call it, God help them. Only there is no pulsation in the

vein." (_De Re Anatomicâ_, Venice, 1559.)

Fabricius ab Aquapendente, Harvey's master at Padua, published his

work on the valves of the veins--_De Venarum Ostiolis_--in 1603. He

did not discover them. Sylvius speaks of them in his _Isagoge_

(Venice, 1555), and they were known to Amatus (1552), and even to

Theodoretus, Bishop of Syria, who lived, as John Hunter said of

Sennertus, "the Lord knows how long ago." But Fabricius studied them

most carefully; and in anatomy he left nothing more to be said about

them. In physiology, his work was of little value; for he held that

they were designed "to retard the blood in some measure, lest it

should run pell-mell into the feet, hands, and fingers, there to be

impacted": they were to prevent distension of the veins, and to ensure

the due nourishment of all parts of the body. It is true that he

compared them to the locks or weirs of a river, but he understood

neither the course nor the force of the blood: as Harvey said of him,

"The man who discovered these valves did not understand their right

use; neither did they who came after him"--_Harum valvularum usum

rectum inventor non est assecutus, nec alii addiderunt; non est enim

ne pondere deorsum sanguis in inferiora totus ruat; sunt namque in

jugularibus deorsum spectantes, et sanguinem sursum ferri

prohibentes._ Men had no idea of the rapidity and volume of the

circulation; they thought of a sort of Stygian tide, oozing this way

or that way in the vessels--Cæsalpinus was of opinion that it went one

way in the daytime and another at night--nor did they see that the

pulmonary circulation and the general circulation are one system, the

same blood covering the whole course. The work that they did in

anatomy was magnificent; Vesalius, and the other great anatomists of

his time, are unsurpassed. But physiology had been hindered for ages

by fantastic imaginings, and the facts of the circulation of the blood

were almost as far from their interpretation in the sixteenth century

as they had been in the time of Galen.

II.--HARVEY (1578-1657)

The _De Motu Cordis et Sanguinis in Animalibus_ was published at

Frankfurt in 1628. And it begins with these words: _Cum multis vivorum

dissectionibus, uti ad manum dabantur_:--

"When by many dissections of living animals, as they came to

hand, I first gave myself to observing how I might discover with

my own eyes, and not from books and the writings of other men,

the use and purpose of the movement of the heart in animals,

forthwith I found the matter hard indeed, and full of

difficulty: so that I began to think, with Frascatorius, that

the movement of the heart was known to God alone. For I could

not distinguish aright either the nature of its systole and

diastole, or when or where dilatation and contraction took

place; and this because of the swiftness of the movement, which

in many animals in the twinkling of an eye, like a flash of

lightning, revealed itself to sight and then was gone; so that I

came to believe that I saw systole and diastole now this way now

the other, and movements now apart and now together. Wherefore

my mind wavered; I had nothing assured to me, whether decided by

me or taken from other men: and I did not wonder that Andreas

Laurentius had written that the movement of the heart was what

the ebb and flow of the Euripus had been to Aristotle.

"At last, having daily used greater disquisition and diligence,

by frequent examination of many and various living

animals--_multa frequenter et varia animalia viva

introspiciendo_--and many observations put together, I came to

believe that I had succeeded, and had escaped and got out of

this labyrinth, and therewith had discovered what I desired, the

movement and use of the heart and the arteries. And from that

time, not only to my friends, but also in public in my

anatomical lectures, after the manner of the Academy, I did not

fear to set forth my opinion in this matter."

It is plain, from Harvey's own words, that he gives to experiments on

animals a foremost place among his methods of work. Take only the

headings of his first four chapters:--

i. _Causæ, quibus ad scribendum auctor permotus fuerit._

ii. _Ex vivorum dissectione, qualis fit cordis motus._

iii. _Arteriarum motus qualis, ex vivorum dissectione._

iv. _Motus cordis et auricularum qualis, ex vivorum

dissectione._

He thrusts it on us, he puts it in the foreground. Read the end of his

Preface:--

"Therefore, from these and many more things of the kind, it is

plain (since what has been said by men before me, of the

movement and use of the heart and arteries, appears inconsistent

or obscure or impossible when one carefully considers it) that

we shall do well to look deeper into the matter; to observe the

movements of the arteries and the heart, not only in man, but in

all animals that have hearts; and by frequent dissection of

living animals, and much use of our own eyes, to discern and

investigate the truth--_vivorum dissectione frequenti, multâque

autopsiâ, veritatem discernere et investigare_."

Finally, take the famous passage in the eighth chapter, _De copiâ

sanguinis transeuntis per cor e venis in arterias, et de circulari

motu sanguinis_:--

"And now, as for the great quantity and forward movement of this

blood on its way, when I shall have said what things remain to

be said--though they are well worth considering, yet they are so

new and strange that I not only fear harm from the envy of

certain men, but am afraid lest I make all men my enemies; so

does custom, or a doctrine once imbibed and fixed down by deep

roots, like second nature, hold good among all men, and

reverence for antiquity constrains them. Be that as it may, the

die is cast now: my hope is in the love of truth, and the

candour of learned minds. I bethought me how great was the

quantity of this blood. Both from the dissection of living

animals for the sake of experiment, with opening of the

arteries, with observations manifold; and from the symmetry of

the size of the ventricles, and of the vessels entering and

leaving the heart--because Nature, doing nothing in vain, cannot

in vain have given such size to these vessels above the

rest--and from the harmonious and happy device of the valves and

fibres, and all other fabric of the heart; and from many other

things--when I had again and again carefully considered it all,

and had turned it over in my mind many times--I mean the great

quantity of the blood passing through, and the swiftness of its

passage--and I did not see how the juices of the food in the

stomach could help the veins from being emptied and drained dry,

and the arteries contrariwise from being ruptured by the

excessive flow of blood into them, unless blood were always

getting round from the arteries into the veins, and so back to

the right ventricle--I began to think to myself whether the

blood had a certain movement, as in a circle--_coepi egomet

mecum cogitare, an motionem quandam quasi in circulo

haberet_--which afterward I found was true."

This vehement passage, which goes with a rush like that of the blood

itself, is a good example of the width and depth of Harvey's work--how

he used all methods that were open to him. He lived to fourscore

years; "an old man," he says, "far advanced in years, and occupied

with other cares": and, near the end of his life, he told the Hon.

Robert Boyle that the arrangement of the valves of the veins had given

him his first idea of the circulation of the blood:--

"I remember that when I asked our famous Harvey, in the only

discourse I had with him, which was but a while before he died,

what were the things which induced him to think of the

circulation of the blood, he answered me that when he took

notice that the valves in the veins of so many parts of the body

were so placed that they gave free passage of the blood towards

the heart, but opposed the passage of the venal blood the

contrary way, he was invited to imagine that so provident a

cause as Nature had not so placed so many valves without design;

and no design seemed more probable than that, since the blood

could not well, because of the interposing valves, be sent by

the veins to the limbs, it should be sent by the arteries, and

return through the veins, whose valves did not oppose its course

that way."

But between this observation, which "invited him to imagine" a theory,

and his final proofs of the circulation, lay a host of difficulties;

and it is certain, from his own account of his work, that experiments

on animals were of the utmost help to him in leading him "out of the

labyrinth."

III.--AFTER HARVEY

1. _The Capillaries_

The capillary vessels were not known in Harvey's time: the

_capillamenta_ of Cæsalpinus were not the capillaries, but the

[Greek: neura] of Aristotle. It was believed that the blood, between

the smallest arteries and the smallest veins, made its way through

"blind porosities" in the tissues, as water percolates through earth

or through a sponge. The first account of the capillaries is in two

letters (_De Pulmonibus_, 1661) from Malpighi, professor of medicine

at Bologna, to Borelli, professor of mathematics at Pisa. In his first

letter, Malpighi writes that he has tried in vain, by injecting the

dead body, to discover how the blood passes from the arteries into the

veins:--

"This enigma hitherto distracts my mind, though for its solution

I have made many and many attempts, all in vain, with air and

various coloured fluids. Having injected ink with a syringe into

the pulmonary artery, I have again and again seen it escape

(become extravasated into the tissues) at several points. The

same thing happens with an injection of mercury. These

experiments do not give us the natural pathway of the blood."

But, in his second letter, he describes how he has examined, with a

microscope of two lenses, the lung and the mesentery of a frog, and

has seen the capillaries, and the blood in them:--

"Such is the divarication of these little vessels, coming off

from the vein and the artery, that the order in which the vessel

ramifies is no longer preserved, but it looks like a network

woven from the offshoots of both vessels."

He was able, in a dead frog, to see the capillaries; and then, in a

living frog, to see the blood moving in them. But, in spite of this

work, it took nearly half a century before Harvey's teaching was

believed by all men--_Tantum consuetudo apud omnes valet_.

2. _The Blood-pressure_

Harvey had seen the facts of blood-pressure--_the great quantity of

blood passing through, and the swiftness of its passage_--but he had

not measured it. Keill's experiments on the blood-pressure (1718) were

inexact, and of no value; and the first exact measurements were made

by Stephen Hales, who was rector of Farringdon, Hampshire, and

minister of Teddington, Middlesex; a Doctor of Divinity, and a Fellow

of the Royal Society. His experiments, in their width and diversity,

were not surpassed even by those of John Hunter, and were extended far

over physiology, vegetable physiology, organic and inorganic

chemistry, and physics; they ranged from the invention of a sea-gauge

to the study of solvents for the stone, and he seems to have

experimented on every force in Nature. The titles of his two volumes

of _Statical Essays_ (1726-1733) show the great extent of his

non-clerical work:--

Volume I. _Statical Essays, containing Vegetable Statics, or an

Account of some Statical Experiments on the Sap in Vegetables,

being an Essay towards a Natural History of Vegetation; also, a

Specimen of an Attempt to Analyse the Air, by a great Variety of

Chymio-Statical Experiments._

Volume II. _Statical Essays, containing Hæmostatics, or an

Account of some Hydraulic and Hydrostatical Experiments made on

the Blood and Blood-vessels of Animals; also, an Account of some

Experiments on Stones in the Kidneys and Bladder, with an

Enquiry into the Nature of those anomalous Concretions._

"We can never want matter for new experiments," he says in his

preface. "We are as yet got little further than to the surface

of things: we must be content, in this our infant state of

knowledge, while we know in part only, to imitate children, who,

for want of better skill and abilities, and of more proper

materials, amuse themselves with slight buildings. The farther

advances we make in the knowledge of Nature, the more probable

and the nearer to truth will our conjectures approach: so that

succeeding generations, who shall have the benefit and advantage

both of their own observations and those of preceding

generations, may then make considerable advances, when _many

shall run to and fro, and knowledge shall be increased_."

His account of his plan of measuring the blood-pressure, and of one of

many experiments that he made on it, is as follows:--

"Finding but little satisfaction in what had been attempted on

this subject by Borellus and others, I endeavoured, about

twenty-five years since, by proper experiments, to find what was

the real force of the blood in the crural arteries of dogs, and

about six years afterwards I repeated the like experiments on

two horses, and a fallow doe; but did not then pursue the matter

any further, being discouraged by the disagreeableness of

anatomical dissections. But having of late years found by

experience the advantage of making use of the statical way of

investigation, not only in our researches into the nature of

vegetables, but also in the chymical analysis of the air, I was

induced to hope for some success, if the same method of enquiry

were applied to animal bodies....

"Having laid open the left crural artery (of a mare), I inserted

into it a brass pipe whose bore was 1/6 of an inch in diameter;

and to that, by means of another brass pipe which was fitly

adapted to it, I fixed a glass tube of nearly the same diameter,

which was 9 feet in length; then, untying the ligature on the

artery, the blood rose in the tube 8 feet 3 inches perpendicular

above the level of the left ventricle of the heart, but it did

not attain to its full height at once: it rushed up gradually

at each pulse 12, 8, 6, 4, 2, and sometimes 1 inch. When it was

at its full height, it would rise and fall at and after each

pulse 2, 3, or 4 inches, and sometimes it would fall 12 or 14

inches, and have there for a time the same vibrations up and

down, at and after each pulse, as it had when it was at its full

height, to which it would rise again, after forty or fifty

pulses."

3. _The Collateral Circulation_

After Hales, came John Hunter, who was five years old when the

_Statical Essays_ were published. His experiments on the blood were

mostly concerned with its properties, not with its course; but one

great experiment must be noted here that puts him in line with Harvey,

Malpighi, and Hales. He got from it his knowledge of the collateral

circulation; he learned how the obstruction of an artery is followed

by enlargement of the vessels in its neighbourhood, so that the parts

beyond the obstruction do not suffer from want of blood: and the facts

of collateral circulation were fresh in his mind when, a few months

later, he conceived and performed his operation for aneurysm (December

1785). The "old operation" gave him no help here; and "Anel's

operation" was but a single instance, and no sure guide for Hunter,

because Anel's patient had a different sort of aneurysm. Hunter knew

that the collateral circulation could be trusted to nourish the limb,

if the femoral artery were ligatured in "Hunter's canal" for the cure

of popliteal aneurysm; and he got this knowledge from the experiment

that he had made on one of the deer in Richmond Park, to see the

influence of ligature of the carotid artery on the growth of the

antler. The following account of this experiment was given by Sir

Richard Owen, who had it from Mr. Clift, Hunter's devoted pupil and

friend:--

"In the month of July, when the bucks' antlers were half-grown,

he caused one of them to be caught and thrown; and, knowing the

arterial supply to the hot 'velvet,' as the keepers call it,

Hunter cut down upon and tied the external carotid; upon which,

laying his hand upon the antler, he found that the pulsations of

the arterial channels stopped, and the surface soon grew cold.

The buck was released, and Hunter speculated on the

result--whether the antler, arrested at mid-growth, would be

shed like the full-grown one, or be longer retained. A week or

so afterward he drove down again to the park, and caused the

buck to be caught and thrown. The wound was healed about the

ligature; but on laying his hand on the antler, he found to his

surprise that the warmth had returned, and the channels of

supply to the velvety formative covering were again pulsating.

His first impression was that his operation had been defective.

To test this, he had the buck killed and sent to Leicester

Square. The arterial system was injected. Hunter found that the

external carotid had been duly tied. But certain small branches,

coming off on the proximal or heart's side of the ligature, had

enlarged; and, tracing-on these, he found that they had

anastomosed with other small branches from the distal

continuation of the carotid, and these new channels had restored

the supply to the growing antler.... Here was a consequence of

his experiment he had not at all foreseen or expected. A new

property of the living arteries was unfolded to him."

All the anatomists had overlooked this physiological change in the

living body, brought about by disease. And the surgeons, since anatomy

could not help them, had been driven by the mortality of the "old

operation" to the practice of amputation.

4. _The Mercurial Manometer_

Hale's experiments on the blood-pressure were admirable in their time;

but neither he nor his successors could take into account all the

physiological and mathematical facts of the case. But a great advance

was made in 1828, when Poiseuille published his thesis, _Sur la Force

du Coeur Aortique_, with a description of the mercurial manometer.

Poiseuille had begun with the received idea that the blood-pressure in

the arteries would vary according to the distance from the heart, but

he found by experiment that this doctrine was wrong:--

"At my first experiments, wishing to make sure whether the

opinions, given _à priori_, were true, I observed to my great

astonishment that two tubes, applied at the same time to two

arteries at different distances from the heart, gave columns of

exactly the same height, and not, as I had expected, of

different heights. This made the work very much simpler,

because, to whatever artery I applied the instrument, I obtained

the same results that I should have got by placing it on the

ascending aorta itself."

He found also, by experiments, that the coagulation of the blood in

the tube could be prevented by filling one part of the tube with a

saturated solution of sodium carbonate. The tube, thus prepared, was

connected with the artery by a fine cannula, exactly fitting the

artery. With this instrument, Poiseuille was able to obtain results

far more accurate than those of Hales, and to observe the diverse

influences of the respiratory movements on the blood-pressure. He sums

up his results in these words:--

"I come to this irrevocable conclusion, that the force with

which a molecule of blood moves, whether in the carotid, or in

the aorta, etc., is exactly equal to the force which moves a

molecule in the smallest arterial branch; or, in other words,

that a molecule of blood moves with the same force over the

whole course of the arterial system--which, _à priori_, with all

the physiologists, I was far from thinking."

And he adds, in a footnote:--

"When I say that this force is the same over the whole course of

the arterial system, I do not mean to deny that it must needs be

modified at certain points of this system, which present a

special arrangement, such as the anastomosing arches of the

mesentery, the arterial circle of Willis, etc."

Later, in 1835, he published a very valuable memoir on the movement of

the blood in the capillaries under different conditions of heat, cold,

and atmospheric pressure.

5. _The Registration of the Blood-pressure_

Poiseuille's work, in its turn, was left behind as physiology went

forward: especially, the discovery of the vaso-motor nerves compelled

physiologists to reconsider the whole subject of the blood-pressure.

If Poiseuille's thesis (1828) be compared with Marey's book (1863),

_Physiologie Médicale de la Circulation du Sang_, it will be evident

at once how much wider and deeper the problem had become. Poiseuille's

thesis is chiefly concerned with mathematics and hydrostatics; it

suggests no method of immediate permanent registration of the pulse,

and is of no great value to practical medicine: Marey's book, by its

very title, shows what a long advance had been made between 1828 and

1863--_Physiologie Médicale de la Circulation du Sang, basée sur

l'étude graphique des mouvements du coeur et du pouls artériel, avec

application aux maladies de l'appareil circulatoire_. Though the

contrast is great between Hales' may-pole and Poiseuille's manometer,

there is even a greater contrast between Poiseuille's mathematical

calculations and Marey's practical use of the sphygmograph for the

study of the blood-pressure in health and disease. Marey had the

happiness of seeing medicine, physiology, and physics, all three of

them working to one end:--

"La circulation du sang est un des sujets pour lesquels la

médecine a le plus besoin de s'éclairer de la physiologie, et où

celle-ci à son tour tire le plus de lumière des sciences

physiques. Ces dernières années sont marquées par deux grands

progrès qui ouvrent aux recherches à venir des horizons

nouveaux: en Allemagne, l'introduction des procédés graphiques

dans l'étude du mouvement du sang; en France, la démonstration

de l'influence du système nerveux sur la circulation

périphérique. Cette dernière découverte, que nous devons à M.

Cl. Bernard, et qui depuis dix ans a donné tant d'impulsion à la

science, montre mieux que toute autre combien la physiologie est

indispensable à la médecine, tandis que les travaux allemands

ont bien fait ressortir l'importance des connaissances physiques

dans les études médicales."

Marey's sphygmograph was not the first instrument of its kind. There

had been, before it, Hérisson's sphygmometer, Ludwig's kymographion,

and the sphygmographs of Volckmann, King, and Vierordt. But, if one

compares a Vierordt tracing with a Marey tracing, it will be plain

that Marey's results were far advanced beyond the useless

"oscillations isochrones" recorded by Vierordt's instrument.

Beside this improved sphygmograph, Chauveau and Marey also invented

the cardiograph, for the observation of the blood-pressure within the

cavities of the heart. Their cardiograph was a set of very delicate

elastic tambours, resting on the heart, or passed through fine tubes

into the cavities of the heart,[1] and communicating impulses to

levers with writing-points. These writing-points, touching a revolving

cylinder, recorded the variations of the endocardial pressure, and the

duration of the auricular and ventricular contractions.

[1] "On peut s'assurer de l'innocuité de ce premier temps de

l'expérience en examinant l'animal, qui n'est nullement troublé,

qui marche et mange comme de coutume. En comptant le chiffre du

pouls, on trouve quelquefois une légère accéleration, surtout dans

les premiers instants; mais les mouvements du coeur sont toujours

réguliers, et donnent, à l'auscultation, des bruits d'un caractère

normal." (Marey, _loc. cit._ p. 63.)

* * * * *

It is impossible here to describe the subsequent study of those more

abstruse problems that the older physiologists had not so much as

thought of: the minutest variations of the blood-pressure, the

multiple influences of the nervous system on the heart and

blood-vessels, the relations between blood-pressure and secretion, the

automatism of the heart-beat, the influence of gravitation, and other

finer and more complex issues of physiology. But, even if one stops at

Marey's book, now more than forty years old, there is an abundant

record of good work, from the discovery of the circulation to the

invention of the sphygmograph.

II

THE LACTEALS

Asellius, in his account of his discovery of the lacteal vessels

(1622), is of opinion that certain of "the ancients" had seen these

vessels, but had not recognised them. He has a great reverence for

authority: Hippocrates, Plato, Aristotle, the Stoics, Herophilus,

Galen, Pollux, Rhases, and a host of other names, he quotes them all,

and all with profound respect; and comes to this conclusion: "It did

not escape the ancients, that certain vessels must needs be concerned

with containing and carrying the chyle, and certain other vessels with

the blood: but the true and very vessels of the chyle, that is, my

'veins,' though they were seen by some of the ancients, yet they were

recognised by none of them." He can forgive them all, except Galen,

_qui videtur nosse omnino debuisse_--"but, as for Galen, I know not at

all what I am to think. For he, who made more than six hundred

sections of living animals, as he boasts himself, and so often opened

many animals when they were lately fed, are we to think it possible

that these veins never showed themselves to him, that he never had

them under his eyes, that he never investigated them--he to whom

Erasistratus had given so great cause for searching out the whole

matter?" Probably, the milk-white threads had been taken for nerves by

those who had seen them: and those who had never seen them, but

believed in their existence, rested their belief on a general idea

that the chyle must, somehow, have vessels of its own apart from the

blood-vessels. What Galen and Erasistratus must have seen, Asellius

and Pecquet discovered: and Harvey gives a careful review of the

discovery in his letters to Nardi (May 1652) and to Morison (November

1653). He does not accept it; but the point is that he recognises it

as a new thing altogether.

A year or two after he had made the discovery, Asellius died; and his

work was published in 1627 by two Milanese physicians, and was

dedicated by them to the senate of the Academy of Milan, where

Asellius had been professor of anatomy. The full title of his book is,

_De Lactibus sive Lacteis Venis, quarto Vasorum Mesaraicorum genere

novo invento, Gasparis Asellii Cremonensis, Anatomici Ticinensis,

Dissertatio. Quâ sententiæ anatomicæ multæ vel perperam receptæ

convelluntur vel partim perceptæ illustrantur._ He gives the following

account of the discovery, in the chapter entitled _Historia primæ

vasorum istorum inventionis cum fide narrata_. On 23rd July 1622,

demonstrating the movement of the diaphragm in a dog, he observed

suddenly, "as it were, many threads, very thin and very white,

dispersed through the whole mesentery and through the intestines, with

ramifications almost endless"--_plurimos, eosque tenuissimos

candido-sissimosque ceu funiculos per omne mesenterium et per

intestina infinitis propemodum propaginibus dispersos_:--

"Thinking at first sight that they were nerves, I did not

greatly heed them. But soon I saw that I was wrong, for I

bethought me that the nerves, which belong to the intestines,

are distinct from these threads, and very different from them,

and have a separate course. Wherefore, struck by the newness of

the matter, I stopped for a time silent, while one way and

another there came to my mind the controversies that occupy

anatomists, as to the mesenteric veins and their use; which

controversies are as full of quarrels as of words. When I had

pulled myself together, to make experiment, taking a very sharp

scalpel, I pierce one of the larger threads. Scarcely had I hit

it off, when I see a white fluid running out, like milk or

cream. At which sight, when I could not hold my joy, turning to

those who were there, first to Alexander Tadinus and Senator

Septalius, both of them members of the most honourable College

of Physicians, and, at the time of this writing, officers of the

public health, '_I have found it_,' I say like Archimedes; and

therewith invite them to the so pleasant sight of a thing so

unwonted; they being agitated, like myself, by the newness of

it."

He then describes the collapse and disappearance of the vessels at

death, and the many experiments which he made for further study of

them; and the failure, when he tried to find them in animals not

lately fed. He did not trace them beyond the mesentery, and believed

that they emptied themselves into the liver. The discovery of their

connection with the receptaculum chyli and the thoracic duct was made

by Jehan Pecquet of Dieppe, Madame de Sévigné's doctor, her "good

little Pecquet." The full title of his book (2nd ed., 1654) is,

_Expérimenta Nova Anatomica, quibus incognitum hactenus Receptaculum,

et ab eo per Thoracem in ramos usque subclavios Vasa Lactea

deteguntur_. He has not the academical learning of Asellius, nor his

obsequious regard for the ancients; and the discovery of the thoracic

duct came, as it were by chance, out of an experiment that was of

itself wholly useless. He had killed an animal by removing its heart,

and then saw a small quantity of milky fluid coming from the cut end

of the vena cava--_Albicantem subinde Lactei liquoris, nec certe parum

fluidi scaturiginem, intra Venæ Cavæ fistulam, circ[=a] dextri sedem

Ventriculi, miror effluere_--and found that this fluid was identical

with the chyle in the lacteals. In another experiment, he succeeded in

finding the thoracic duct--"At last, by careful examination deep down

along the sides of the dorsal vertebræ, a sort of whiteness, as of a

lacteal vessel, catches my eyes. It lay in a sinuous course, close up

against the spine. I was in doubt, for all my scrutiny, whether I had

to do with a nerve or with a vessel. Therefore, I put a ligature a

little below the clavicular veins; and then the flaccidity above the

ligature, and the swelling of the distended duct below the ligature,

broke down my doubt--_Ergo subducto paulo infra Claviculas vinculo,

cum a ligaturâ sursum flaccesceret, superstite deorsum turgentis

alveoli tumore, dubium meum penitus enervavit.... Laxatis vinculis,

lacteus utrinque rivulus in Cavam affatim Chylum profudit._"

It is to be noted that Asellius and Pecquet, both of them, made their

discoveries as it were by chance. Unless digestion were going on, the

lacteals would be empty and invisible; and, on the dead body,

lacteals, receptaculum, and thoracic duct would all be empty. For

these reasons, it cost a vast number of experiments to prove the

existence, and to discover the course, of these vessels. Once found in

living animals, they could be injected and dissected in the dead body;

but they had been overlooked by Vesalius and the men of his time.

From the discovery of the lacteals came the discovery of the whole

lymphatic system. Daremberg, in his _Histoire des Sciences Médicales_

(Paris, 1870), after an account of Pecquet's work, says:--

"Up to this point, we have seen English, Italians, and French

working together, with more or less success and genius, to trace

the true ways of blood and chyle: there is yet one field of work

to open up, the lymphatics of the body. The chief honour here

belongs, without doubt, to the Swede Rudbeck, though the Dane

Bartholin has disputed it with him, with equal acrimony and

injustice."

Rudbeck's work (1651-54) coincides exactly, in point of time, with the

first and second editions, 1651 and 1654, of Pecquet's _De Lactibus_.

It may be said, therefore, that the whole doctrine of the lymphatic

system was roughed out half-way through the seventeenth century.

III

THE GASTRIC JUICE

From many causes, the experimental study of the digestive processes

came later than the study of the circulation. As an object of

speculative thought, digestion was a lower phase of life, the work of

crass spirits, less noble than the blood; from the point of view of

science, it could not be studied ahead of organic chemistry, and got

no help from any other sort of knowledge; and, from the medical point

of view, it was the final result of many unknown internal forces that

could not be observed or estimated either in life or after death. It

did not, like the circulation, centre itself round one problem; it

could not be focussed by the work of one man. For these reasons, and

especially because of its absolute dependence on chemistry for the

interpretation of its facts, it had to bide its time; and Réaumur's

experiments are separated from the publication of Harvey's _De Motu

Cordis et Sanguinis_ by a hundred and thirty years.

The following account of the first experiments on digestion is taken

from Claude Bernard's _Physiologie Opératoire_, 1879:--

"The true experimental study of digestion is of comparatively

recent date; the ancients were content to find comparisons, more

or less happy, with common facts. Thus, for Hippocrates,

digestion was a 'coction': for Galen, a 'fermentation,' as of

wine in a vat. In later times, van Helmont started this

comparison again: for him, digestion was a fermentation like

that of bread: as the baker, having kneaded the bread, keeps a

little of the dough to leaven the next lot kneaded, so, said van

Helmont, the intestinal canal never completely empties itself,

and the residue that it keeps after each digestion becomes the

leaven that shall serve for the next digestion.

"The first experimental studies on the digestion date from the

end of the seventeenth century, when the Academy of Florence was

the scene of a famous and long controversy between Borelli and

Valisnieri. The former saw nothing more in digestion than a

purely mechanical act, a work of attrition whereby the ingesta

were finely divided and as it were pulverised: and in support of

this opinion Borelli invoked the facts that he had observed

relating to the gizzard of birds. We know that this sac, with

its very thick muscular walls, can exercise on its contents

pressure enough to break the hardest bodies. Identifying the

human stomach with the bird's gizzard, Borelli was led to

attribute to the walls of the stomach an enormous force,

estimated at more than a thousand pounds; whose action, he said,

was the very essence of digestion. Valisnieri, on the contrary,

having had occasion to open the stomach of an ostrich, had found

there a fluid which seemed to act on bodies immersed in it; this

fluid, he said, was the active agent of digestion, a kind of

_aqua fortis_ that dissolved food.

"These two opposed views, resulting rather from observations

than from regularly instituted experiments, were the

starting-point of the experimental researches undertaken by

Réaumur in 1752. To resolve the problem set by Borelli and

Valisnieri, Réaumur made birds swallow food enclosed in

fenestrated tubes, so that the food, protected from the

mechanical action of the walls of the stomach, was yet exposed

to the action of the gastric fluid. The first tubes used

(glass, tin, etc.) were crushed, bent, or flattened by the

action of the walls of the gizzard; and Réaumur failed to oppose

to this force a sufficient resistance, till he employed leaden

tubes thick enough not to be flattened by a pressure of 484

pounds: which was, in fact, the force exercised by the

contractile walls of the gizzard in turkeys, ducks, and fowls

under observation. These leaden tubes--filled with ordinary

grain, and closed only by a netting that let pass the gastric

juices--these tubes, after a long stay in the stomach, still

enclosed grain wholly intact, unless it had been crushed before

the experiment. When they were filled with meat, it was found

changed, but not digested. Réaumur was thus led at first to

consider digestion, in the gallinaceæ, as pure and simple

trituration. But, repeating these experiments on birds of prey,

he observed that digestion in them consists essentially in

dissolution, without any especial mechanical action, and that it

is the same with the digestion of meat in all animals with

membranous stomachs. To procure this dissolving fluid, Réaumur

made the birds swallow sponges with threads attached:

withdrawing these sponges after a definite period, he squeezed

the fluid into a glass, and tested its action on meat. That was

the first attempt at artificial digestion _in vitro_. He did not

carry these last investigations very far, and did not obtain

very decisive results; nevertheless he must be considered as the

discoverer of artificial digestion."

After Réaumur, the Abbé Spallanzani (1783) made similar observations

on many other animals, including carnivora. He showed that even in the

gallinaceæ there was dissolution of food, not mere trituration: and

observed how after death the gastric fluid may under certain

conditions act on the walls of the stomach itself.

"Henceforth the experimental method had cut the knot of the

question raised by the theories of Borelli and Valisnieri:

digestion could no longer be accounted anything but a

dissolution of food by the fluid of the stomach, the gastric

juice. But men had still to understand this gastric juice, and

to determine its nature and mode of action. Nothing could be

more contradictory than the views on this matter. Chaussier and

Dumas, of Montpellier, regarded the gastric juice as of very

variable composition, one time alkaline, another acid, according

to the food ingested. Side by side with these wholly theoretical

opinions, certain results of experiments had led to ideas just

as erroneous, for want of rigorous criticism of methods; it was

thus that Montègre denied the existence of the gastric juice as

a special fluid; what men took for gastric juice, he said, was

nothing but the saliva turned acid in the stomach. To prove his

point, he made the following experiment:--He masticated a bit of

bread, then put it out on a plate; it was at first alkaline,

then at the end of some time it became acid. In those days

(1813) this experiment was a real embarrassment to the men who

believed in the existence of a special gastric juice: we have

now no need to refute it.

"These few instances suffice to show how the physiologists were

unsettled as to the nature and properties of the gastric juice.

Then (1823) the Academy had the happy idea of proposing

digestion as a subject for a prize. Tiedemann and Gmelin in

Germany, Leuret and Lassaigne in France, submitted works of

equal merit, and the Academy divided the prize between them. The

work of Tiedemann and Gmelin is of especial interest to us on

account of the great number of their experiments, from which

came not only the absolute proof of the existence of the gastric

juice, but also the study of the transformation of starch into

glucose. Thus the theory of digestion entered a new phase: it

was finally recognised, at least for certain substances, that

digestion is not simply dissolution, but a true chemical

transformation." (Cl. Bernard, _loc. cit._)

In 1825 Dr. William Beaumont, a surgeon in the United States Army,

began his famous experiments on Alexis St. Martin, a young Canadian

travelling for the American Fur Company, who was shot in the abdomen

on 6th June 1822, and recovered, but was left with a permanent opening

in his stomach. Since the surgery of those days did not favour an

operation to close this fistula, Dr. Beaumont took St. Martin into his

service, and between 1825 and 1833 made a vast number of experiments

on him. These he published,[2] and they were of great value. But it is

to be noted that the ground had been cleared already, fifty years

before, by Réaumur and Spallanzani:--

"_I make no claim to originality in my opinions_, as it respects

the existence and operation of the gastric juice. My experiments

confirm the doctrines (with some modifications) taught by

Spallanzani, and many of the most enlightened physiological

writers." (Preface to Dr. Beaumont's book.)

[2] _Experiments and Observations on the Gastric Juice, and the

Physiology of Digestion_, by William Beaumont, M.D.; Edinburgh,

1838.

Further, it is to be noted that Alexis St. Martin's case proves that a

gastric fistula is not painful. Scores of experiments were made on

him, off and on, for nine years:--

"During the whole of these periods, from the spring of 1824 to

the present time (1833), he has enjoyed general good health, and

perhaps suffered much less predisposition to disease than is

common to men of his age and circumstances in life. He has been

active, athletic, and vigorous; exercising, eating, and drinking

like other healthy and active people. For the last four months

he has been unusually plethoric and robust, though constantly

subjected to a continuous series of experiments on the interior

of the stomach; allowing to be introduced or taken out at the

aperture different kinds of food, drinks, elastic catheters,

thermometer tubes, gastric juice, chyme, etc., almost daily, and

sometimes hourly.

"Such have been this man's condition and circumstances for

several years past; and he now enjoys the most perfect health

and constitutional soundness, with every function of the system

in full force and vigour." (Dr. Beaumont, _loc. cit_. p. 20.)

In 1834 Eberlé published a series of observations on the extraction of

gastric juice from the mucous membrane of the stomach after death; in

1842 Blondlot of Nancy studied the gastric juice of animals by the

method of a fistula, such as Alexis St. Martin had offered for Dr.

Beaumont's observation. After Blondlot, came experiments on the

movements of the stomach, and on the manifold influences of the

nervous system on digestion.

It has been said, times past number, that an animal with a fistula is

in pain. It is not true. The case of St. Martin is but one out of a

multitude of these cases: an artificial orifice of this kind is not

painful.

IV

GLYCOGEN

Claude Bernard's discovery of glycogen in the liver had a profound

influence both on physiology and on pathology. Take first its

influence on pathology. Diabetes was known to Celsus, Aretæus, and

Galen; Willis, in 1674, and Morton, in 1675, noted the distinctive

sweetness of the urine; and their successors proved the presence of

sugar in it. Rollo, in 1787, observed that vegetable food was bad for

diabetic patients, and introduced the strict use of a meat diet. But

Galen had believed that diabetes was a disease of the kidneys, and

most men still followed him: nor did Rollo greatly advance pathology

by following not Galen, but Aretæus. Later, with the development of

organic chemistry, came the work of Chevreuil (1815), Tiedemann and

Gmelin (1823), and other illustrious chemists: and the pathology of

diabetes grew more and more difficult:--

"These observations gave rise to two theories: the one, that

sugar is formed with abnormal rapidity in the intestine,

absorbed into the blood, and excreted in the urine; the other,

that diabetes is due to imperfect destruction of the sugar,

either in the intestine or in the blood. Some held that it

underwent conversion into lactic acid as it was passing through

the intestinal walls, while others believed it to be destroyed

in the blood by means of the alkali therein contained."[3]

[3] _Reynolds' System of Medicine_, vol. v., art. "Diabetes

Mellitus."

Thus, before Claude Bernard (1813-1878), the pathology of diabetes was

almost worthless. And, in physiology, his work was hardly less

important than the work of Harvey. A full account of it, in all its

bearings, is given in Sir Michael Foster's _Life of Claude Bernard_

(Fisher Unwin, 1899).

In Bernard's _Leçons sur le Diabète et la Glycogenèse Animale_ (Paris,

1877), there is a sentence that has been misquoted many times:--

_Sans doute, nos mains sont vides aujourd'hui, mais notre bouche peut

être pleine de légitimes promesses pour l'avenir._

This sentence has been worked so hard that some of the words have got

rubbed off it: and the statement generally made is of this kind:--

_Claude Bernard himself confessed that his hands were empty, but his

mouth was full of promises._

Of course, he did not mean that he was wrong in his facts. But, in

this particular lecture, he is speaking of the want of more science in

practice, looking forward to a time when treatment should be based on

science, not on tradition. Medicine, he says, is neither science nor

art. Not science--_Trouverait-on aujourd'hui un seul médecin

raisonnable et instruit osant dire qu'il prévoit d'une manière

certaine la marche et l'issue d'une maladie ou l'effet d'une remède?_

Not art, because art has always something to show for its trouble: a

statue, a picture, a poem--_Le médecin artiste ne crée rien, et ne

laisse aucune oeuvre d'art, à moins d'appliquer ce titre à la guérison

du malade. Mais quand le malade meurt, est-ce également son oeuvre? Et

quand il guérit, peut-il distinguer sa part de celle de la nature?_

To Claude Bernard, experiments on animals for the direct advancement

of medicine seemed a new thing: new, at all events, in comparison with

the methods of some men of his time. He was only saying what Sir John

Burdon Sanderson said in 1875 to the Royal Commission:--

_It is my profound conviction that a future will come, it may be a

somewhat distant future, in which the treatment of disease will be

really guided by science. Just as completely as mechanical science has

come to be the guide of the mechanical arts, do I believe, and I feel

confident, that physiological science will eventually come to be the

guide of medicine and surgery._

Anyhow, lecturing a quarter of a century ago on diabetes, his special

subject, Claude Bernard spoke out his longing to compel men into the

ways of science, to give them some immediate sign which they could not

refuse to see:--

"At this present time, medicine is passing from one period to

another. The old traditions are losing ground, and scientific

medicine (_la médecine expérimentale_) has got hold of all our

younger men: every day it gains ground, and will establish

itself against all its critics, and in spite of the excesses of

those who are over-zealous for its honour.... And when men ask

us what are the results of scientific medicine, we are driven to

answer that it is scarcely born, that it is still in the making.

Those who care for nothing but an immediate practical

application must remember Franklin's words, _What is the use of

a new-born child, but to become a man?_ If you deliberately

reject scientific medicine, you fail to see the natural

development of man's mind in all the sciences. Without doubt,

our hands are empty to-day, but our mouth may well be filled

with legitimate promises for the future."

He died in 1878. The following account of the discovery of glycogen is

taken from his _Nouvelle Fonction du Foie_ (Paris, 1853):--

"My first researches into the assimilation and destruction of

sugar in the living organism were made in 1843: and in my

inaugural thesis (Dec. 1843) I published my first experiments on

the subject. I succeeded in demonstrating a fact hitherto

unknown, that cane-sugar cannot be directly destroyed in the

blood. If you inject even a very small quantity of cane-sugar,

dissolved in water, into the blood or under the skin of a

rabbit, you find it again in the urine unchanged, with all its

chemical properties the same.... I had soon to give up my first

point of view, because this question of the existence of a

sugar-producing organ, that I had thought such a hard problem of

physiology, was really the first thing revealed to me, as it

were of itself, at once."

He kept two dogs on different diets, one with sugar, the other without

it; then killed them during digestion, and tested the blood in the

hepatic veins:--

"What was my surprise, when I found a considerable quantity of

sugar in the hepatic veins of the dog that had been fed on meat

only, and had been kept for eight days without sugar: just as I

found it in the other dog that had been fed for the same time on

food rich in sugar....

"Finally, after many attempts--_après beaucoup d'essais et

plusieurs illusions que je fus obligé de rectifier par des

tâtonnements_--I succeeded in showing, that in dogs fed on meat

the blood passing through the portal vein does not contain sugar

before it reaches the liver; but when it leaves the liver, and

comes by the hepatic veins into the inferior vena cava, this

same blood contains a considerable quantity of a sugary

substance (glucose)."

His further discovery, that this formation of sugar is increased by

puncture of the floor of the fourth ventricle, was published in 1849.

It is impossible to exaggerate the importance of Claude Bernard's

single-handed work in this field of physiology and pathology:--

"As a mere contribution to the history of sugar within the

animal body, as a link in the chain of special problems

connected with digestion and nutrition, its value was very

great. Even greater, perhaps, was its effect as a contribution

to general views. The view that the animal body, in contrast to

the plant, could not construct, could only destroy, was, as we

have seen, already being shaken. But evidence, however strong,

offered in the form of numerical comparisons between income and

output, failed to produce anything like the conviction which was

brought home to every one by the demonstration that a substance

was actually formed within the animal body, and by the

exhibition of the substance so formed.

"No less revolutionary was the demonstration that the liver had

other things to do in the animal economy besides secreting bile.

This, at one blow, destroyed the then dominant conception that

the animal body was to be regarded as a bundle of organs, each

with its appropriate function, a conception which did much to

narrow inquiry, since when a suitable function had once been

assigned to an organ there seemed no need for further

investigations....

"No less pregnant of future discoveries was the idea suggested

by this newly-found-out action of the hepatic tissue, the idea

happily formulated by Bernard as 'internal secretion.' No part

of physiology is at the present day being more fruitfully

studied than that which deals with the changes which the blood

undergoes as it sweeps through the several tissues, changes by

the careful adaptation of which what we call the health of the

body is secured, changes the failure or discordance of which

entails disease. The study of these internal secretions

constitutes a path of inquiry which has already been trod with

conspicuous success, and which promises to lead to untold

discoveries of the greatest moment; the gate to this path was

opened by Bernard's work." (Sir M. Foster, _loc. cit._)

But the work to be done, before all the clinical facts of the disease

can be stated in terms of physiology, is not yet finished. In England,

especial honour is due to Dr. Pavy for his life-long study of this

most complex problem.

V

THE PANCREAS

Here again Claude Bernard's name must be put first. Before him, the

diverse actions of the pancreatic juice had hardly been studied.

Vesalius, greatest of all anatomists, makes no mention of the duct of

the pancreas, and speaks of the gland itself as though its purpose

were just to support the parts in its neighbourhood--_ut ventriculo

instar substerniculi ac pulvinaris subjiciatur_. The duct was

discovered by Wirsung, in 1642: but anatomy could not see the things

that belong to physiology. Lindanus (1653) said, _I cannot doubt that

the pancreas expurgates, in the ordinary course of Nature, those

impurities of the blood that are too crass and inept to be tamed by

the spleen: and, in the extraordinary course, all black bile, begotten

of disease or intemperate living_. Wharton (1656) said, _It ministers

to the nerves, taking up certain of their superfluities, and remitting

them through its duct into the intestines_. And Tommaso Bartholini

(1666) called it the _biliary vesicle of the spleen_.

This chaos of ideas was brought into some sort of order by Regnier de

Graaf, pupil of François de Bois (Sylvius). De Bois had guessed that

the pancreas must be considered not according to its position in the

body, but according to its structure: that it was analogous to the

salivary glands. He urged his pupil to make experiments on it: and de

Graaf says:--

"I put my hand to the work: and though many times I despaired of

success, yet at last, by the blessing of God on my work and

prayers, in the year 1660 I discovered a way of collecting the

pancreatic juice."

And, by further experiment, he refuted Bartholini's theory that the

pancreas was dependent on the spleen.

Sylvius had supposed that the pancreatic juice was slightly acid, and

de Graaf failed to note this mistake; but it was corrected by Bohn's

experiments in 1710.

Nearly two hundred years come between Regnier de Graaf and Claude

Bernard: it is no wonder that Sir Michael Foster says that de Graaf's

work was "very imperfect and fruitless." So late as 1840, there was

yet no clear understanding of the action of the pancreas. Physiology

could not advance without organic chemistry; de Graaf could no more

discover the amylolytic action of the pancreatic juice than Galvani

could invent wireless telegraphy. The physiologists had to wait till

chemistry was ready to help them:--

"Of course, while physical and chemical laws were still lost in

a chaos of undetermined facts, it was impossible that men should

analyse the phenomena of life: first, because these phenomena go

back to the laws of chemistry and physics; and next, because

they cannot be studied without the apparatus, instruments, and

all other methods of analysis that we owe to the laboratories of

the chemists and the physicists." (Cl. Bernard, _Phys. Opér._,

p. 61.)

Therefore de Graaf failed, because he got no help from other sciences.

But it cannot be called failure; he must be contrasted with the men

of his time, Lindanus and Bartholini, facts against theories, not with

men of this century. And Claude Bernard went back to de Graaf's method

of the fistula, having to guide him the facts of chemistry observed by

Valentin, Tiedemann and Gmelin, and Eberlé. His work began in 1846,

and the Académie des Sciences awarded a prize to it in 1850:--

"Let this vague conception (the account of the pancreas given in

Johannes Müller's Text-book of Physiology) be compared with the

knowledge which we at present have of the several distinct

actions of the pancreatic juice, and of the predominant

importance of this fluid not only in intestinal digestion but in

digestion as a whole, and it will be at once seen what a great

advance has taken place in this matter since the early forties.

That advance we owe in the main to Bernard. Valentin, it is

true, had in 1844 not only inferred that the pancreatic juice

had an action on starch, but confirmed his view by actual

experiment with the juice expressed from the gland; and Eberlé

had suggested that the juice had some action on fat; but Bernard

at one stroke made clear its threefold action. He showed that it

on the one hand emulsified, and on the other hand split up, into

fatty acids and glycerine, the neutral fats; he clearly proved

that it had a powerful action on starch, converting it into

sugar; and lastly, he laid bare its remarkable action on proteid

matters." (Sir Michael Foster, _loc. cit._)

Finally came the discovery that the pancreas--apart from its

influences on digestion--contributes its share, like the ductless

glands, to the general chemistry of the body:--

"It was discovered, a few years ago, by von Mering and

Minkowski, that if, instead of merely diverting its secretion,

the pancreas is bodily removed, the metabolic processes of the

organism, and especially the metabolism of carbo-hydrates, are

entirely deranged, the result being the production of permanent

diabetes. But if even a very small part of the gland is left

within the body, the carbo-hydrate metabolism remains unaltered,

and there is no diabetes. The small portion of the organ which

has been allowed to remain (and which need not even be left in

its proper place, but may be transplanted under the skin or

elsewhere) is sufficient, by the exchanges which go on between

it and the blood generally, to prevent those serious

consequences to the composition of the blood, and the general

constitution of the body, which result from the complete removal

of this organ." (Prof. Schäfer, 1894.)

Here, in this present study of "pancreatic diabetes," by Dr. Vaughan

Harley and others, are facts as important as any that Bernard made

out: in no way contradicting his work, but adding to it. The pancreas

is no longer taken to be only a sort of salivary gland out of place:

over and above the secretion that it pours into the intestines, it has

an "internal secretion," a constituent of the blood: it belongs not

only to the digestive system, but also, like the thyroid gland and the

suprarenal capsules, to the whole chemistry of the blood and the

tissues. So far has physiology come, unaided by anatomy, from the

fantastic notions of Lindanus and the men of his time: and has come

every inch of the way by the help of experiments on animals. Professor

Starling's observations, on the chemical influence of the duodenal

mucous membrane on the flow of pancreatic fluid, have advanced the

subject still further.

VI

THE GROWTH OF BONE

The work of du Hamel proved that the periosteum is one chief agent in

the growth of bone. Before him, this great fact of physiology was

unknown; for the experiments made by Anthony de Heide (1684), who

studied the production of callus in the bones of frogs, were wholly

useless, and serve only to show that men in his time had no clear

understanding of the natural growth of bone. De Heide says of his

experiments:--

"From these experiments it appears--_forsan probatur_--that

callus is generated by extravasated blood, whose fluid particles

being slowly exhaled, the residue takes the form of the bone:

which process may be further advanced by deciduous halitus from

the ends of the broken bone."

And Clopton Havers, in his _Osteologia Nova_ (London, 1691), goes so

far the wrong way that he attributes to the periosteum not the

production of bone, but the prevention of over-production; the

periosteum, he says, is put round the shaft of a bone to compress it,

lest it grow too large.

Du Hamel's discovery (1739-1743) came out of a chance observation,

made by John Belchier,[4] that the bones of animals fed near

dye-works were stained with the dye. Belchier therefore put a bird on

food mixed with madder, and found that its bones had taken up the

stain. Then du Hamel studied the whole subject by a series of

experiments. To estimate the advance that he gave to physiology,

contrast de Heide's fanciful language with the title of one of du

Hamel's papers--_Quatrième Mémoire sur les Os, dans lequel on se

propose de rapporter de nouvelles preuves qui établissent que les os

croissent en grosseur par l'addition de couches osseuses qui tirent

leur origine du périoste, comme le corps ligneux des Arbres augmente

en grosseur par l'addition de couches ligneuses qui se forment dans

l'écorce._ Or take an example of du Hamel's method:--

"Three pigs were destined to clear up my doubts. The first, six

weeks old, was fed for a month on ordinary food, with an ounce

daily of madder-juice--_garence grappe_--put in it. At the end

of the month, we stopped the juice, and fed the pig in the

ordinary way for six weeks, and then killed it. The marrow of

the bones was surrounded by a fairly thick layer of white bone:

this was the formation of bone during the first six weeks of

life, without madder. This ring of white bone was surrounded by

another zone of red bone: this was the formation of bone during

the administration of the madder. Finally, this red zone was

covered with a fairly thick layer of white bone: this was the

layer formed after the madder had been left off.... We shall

have no further difficulty in understanding whence transudes the

osseous juice that was thought necessary for the formation of

callus and the filling-up of the wounds of the bones, now we see

that it is the periosteum that fills up the wounds, or is made

thick round the fractures, and afterward becomes of the

consistence of cartilage, and at last acquires the hardness of

bones."

[4] "An Account of the Bones of Animals being changed to a Red

Colour by Aliment only," by John Belchier, F.R.S., _Phil. Trans.

Roy. Soc._, 1735-36. There is a letter from Sir Hans Sloane, then

President of the Royal Society, to M. Geoffroy, member of the

French Academy:--"M. Belchier, chirurgien, membre de cette

Société, dînant un jour chez un Teinturier qui travaille en Toiles

peintes, remarqua que dans un Porc frais qu'on avoit servi sur

table, et dont la chair étoit de bon goût, les os étoient rouges.

Il demanda la cause d'un effet si singulier, et on lui dit que ces

sortes de Teinturiers se servoient de la racine de Rubia

Tinctorum, ou garence, pour fixer les couleurs déjà imprimées sur

les Toiles de coton, qu'on appelle en Angleterre callicoes." This

passage of dye into the bones of animals had been noted so far

back as 1573, by Antoine Mizald, a doctor in Paris--_Erythrodanum,

vulgo rubia tinctorum, ossa pecudum rubenti et sandycino colore

imbuit._

These results, confirmed by Bazan (1746) and Boehmer (1751), were far

beyond anything that had yet been known about the periosteum. But the

growth of bone is a very complex process: the naked eye sees only the

grosser changes that come with it; and du Hamel's ingenious comparison

between the periosteum and the bark of trees was too simple to be

exact. Therefore his work was opposed by Haller, and by Dethleef,

Haller's pupil: and the great authority of Haller's name, and the

difficulties lying beyond du Hamel's plain facts, brought about a long

period of uncertainty. Bordenave (1756) found reasons for supporting

Haller; and Fougeroux (1760) supported du Hamel. Thus men came to

study the whole subject with more accuracy--the growth in length, as

well as the growth in thickness; the medullary cavity, the development

of bone, the nutrition and absorption of bone. Among those who took up

the work were Bichat, Hunter, Troja, and Cruveilhier; and they

recognised the surgical aspect of these researches in physiology.

After them, the periosteal growth of bone became, as it were, a part

of the principles of surgery. From this point of view of practice,

issued the experiments made by Syme (1837) and Stanley (1849): which

proved the importance of the epiphysial cartilages for the growth of

the bones in length, and the risk of interfering with these

cartilages in operations on the joints of children. Finally, with the

rise of anæsthetics and of the antiseptic method, came the work of

Ollier, of Lyon, whose good influence on the treatment of these cases

can hardly be over-estimated.

VII

THE NERVOUS SYSTEM

As with the circulatory system, so with the nervous system, the work

of Galen was centuries ahead of its time. Before him, Aristotle, who

twice refers to experiments on animals, had observed the brain during

life: for he says, "In no animal has the blood any feeling when it is

touched, any more than the excretions; nor has the brain, or the

marrow, any feeling, when it is touched": but there is reason for

believing that he neither recognised the purpose of the brain, nor

understood the distribution of the nerves. Galen, by the help of the

experimental method, founded the physiology of the nervous system:--

"Galen's method of procedure was totally different to that of an

anatomist alone. He first reviewed the anatomical position, and

by dissection showed the continuity of the nervous system, both

central and peripheral, and also that some bundles of nerve

fibres were distributed to the skin, others to the muscles.

Later, by process of the physiological experiment of dividing

such bundles of fibres, he showed that the former were sensory

fibres and the latter motor fibres. He further traced the nerves

to their origins in the spinal cord, and their terminations as

aforesaid. From these observations and experiments he was able

to deduce the all-important fact that different nerve-roots

supplied different groups of muscles and different areas of the

skin.... An excellent illustration of his method, and of the

fact that we ought not to treat symptoms, but the causes of

symptoms, is shown very clearly in one of the cases which Galen

records as having come under his care. He tells us that he was

consulted by a certain sophist called Pausanias, who had a

severe degree of anæsthesia of the little and ring fingers. For

this loss of sensation, etc., the medical men who attended him

applied ointments of various kinds to the affected fingers; but

Galen, considering that that was a wrong principle, inquired

into the history, and found that while the patient was driving

in his chariot he had accidentally fallen out and struck his

spine at the junction of the cervical and dorsal regions. Galen

recognised that he had to do with a traumatism affecting the

eighth cervical and first dorsal nerve; therefore, he says, he

ordered that the ointments should be taken off the hand and

placed over the spinal column, so as to treat the really

affected part, and not apply remedies to merely the referred

seat of pain."[5]

[5] From an address on Galen, given by Sir Victor Horsley before

the Medical Society of the Middlesex Hospital. See _Middlesex

Hospital Journal_, May 1899.

Galen, by this sort of work, laid the foundations of physiology; but

the men who came after him let his facts be overwhelmed by fantastic

doctrines: all through the ages, from Galen to the Renaissance, no

great advance was made toward the interpretation of the nervous

system. Long after the Renaissance, his authority still held good; his

ghost was not laid even by Paracelsus and Vesalius, it haunted the

medical profession so late as the middle of the seventeenth century;

but the men who worshipped his name missed the whole meaning of his

work. This long neglect of the experimental method left such a gap in

the history of physiology, that Sir Charles Bell seems to take up the

experimental study of the nervous system at the point where Galen had

stopped short; we go from the time of Commodus to the time of George

the Third, and there is Bell, as it were, putting the finishing touch

to Galen's facts. It is true that experiments had been made on the

nervous system by many men; but a dead weight of theories kept down

the whole subject. For a good instance, how imagination hindered

science, there is the following list, made by Dr. Risien Russell, of

theories about the cerebellum:--

"Galen was of opinion that the cerebellum must be the originator

of a large amount of vital force. After him, and up to the time

of Willis, the prevalent idea seems to have been that it was the

seat of memory; while Bourillon considered it the seat of

instinct and intelligence. Willis supposed that it presided over

involuntary movements and organic functions; and this view,

though refuted by Haller, continued in the ascendency for some

time. Some believed strongly in its influence on the functions

of organic life; and according to some, diseases of the

cerebellum appeared to tell on the movements of the heart....

Haller believed it to be the seat of sensations, as well as the

source of voluntary power; and there were many supporters of the

theory that the cerebellum was the seat of the sensory centres.

Renzi considered this organ the nervous centre by which we

perceive the reality of the external world, and direct and fix

our senses on the things round us. Gall, and later Broussais,

and others, held that this organ presided over the instinct of

reproduction, or the propensity to love; while Carus regarded it

as the seat of the will also. Rolando looked on it as the source

of origin of all movements. Jessen adduced arguments in favour

of its being the central organ of feeling, or of the soul, and

the principal seat of the sensations."

It is plain, from this list, that physiology had become obscured by

fanciful notions of no practical value. If a better understanding of

the nervous system could have been got without experiments on

animals, why had men to wait so long for it? The Italian anatomists

had long ago given them all the anatomy that was needed to make a

beginning; the hospitals, and practice, had given them many hundred

years of clinical facts; nervous diseases and head injuries were

common enough in the Middle Ages; and by the time of Ambroise Paré, if

not before, _post-mortem_ examinations were allowed. The one thing

wanted was the experimental method; and, for want of it, the science

of the nervous system stood still. Experiments had been made; but the

steady, general, unbiassed use of this method had been lost sight of,

and men were more occupied with logic and with philosophy.

Then, in 1811, came Sir Charles Bell's work. If any one would see how

great was the need of experiments on animals for the interpretation of

the nervous system, let him contrast the physiology of the eighteenth

century with that one experiment by Bell which enabled him to say, "I

now saw the meaning of the double connection of the nerves with the

spinal marrow." It is true that this method is but a part of the

science of medicine; that experiment and experience ought to go

together like the convexity and the concavity of a curve. But it is

true also that men owe their deliverance from ignorance about the

nervous system more to experiments on animals than to any other method

of observing facts.

1. _Sir Charles Bell_ (1778-1842)

The great authority of Sir Charles Bell has been quoted a thousand

times against all experiments on animals:--

"Experiments have never been the means of discovery; and a

survey of what has been attempted of late years in physiology,

will prove that the opening of living animals has done more to

perpetuate error than to confirm the just views taken from the

study of anatomy and natural motions."

He wrote, of course, in the days before bacteriology, before

anæsthetics; he had in his mind neither inoculations, nor any

observations made under chloroform or ether, but just "the opening of

living animals." He had also in his mind, and always in it, a great

dislike against the school of Magendie. Let all that pass; our only

concern here is to know whether these words are true of his own work.

They occur in a paper, _On the Motions of the Eye, in Illustration of

the Uses of the Muscles and Nerves of the Orbit_; communicated by Sir

Humphry Davy to the Royal Society, and read March 20, 1823.[6] This

essay was one of a series of papers on the nervous system, presented

to the Royal Society during the years 1821-1829. In 1830, having

already published four of these papers under the title, _The

Exposition of the Nervous System_, Bell published all six of them,

under the title, _The Nervous System of the Human Body_.

[6] This paper includes an _Experimental Enquiry into the Action

of these Muscles_, giving an account of an experiment on the eye.

In his Preface to this book (1830) he quotes the earliest of all his

printed writings on the nervous system, a pamphlet, printed in 1811,

under the title, _An Idea of a New Anatomy of the Brain, Submitted for

the Observation of the Authors Friends_. We have therefore two

statements of his work, one in 1811, the other in 1823 and 1830. The

first of them was written when his work was still new before his

eyes.

Those who say that experiments did not help Bell in his great

discovery--the difference between the anterior and the posterior

nerve-roots--appeal to certain passages in the 1830 volume:--

"In a foreign review of my former papers, the results have been

considered as a further proof in favour of experiments. They

are, on the contrary, deductions from anatomy; and I have had

recourse to experiments, not to form my own opinions, but to

impress them upon others. It must be my apology that my utmost

efforts of persuasion were lost, while I urged my statements on

the grounds of anatomy alone. I have made few experiments; they

have been simple and easily performed, and I hope are

decisive....

"My conceptions of this matter arose by inference from the

anatomical structure; so that the few experiments which have

been made were directed only to the verification of the

fundamental principles on which the system is established."

If it were not for the 1811 pamphlet, the opponents of all experiments

on animals might claim Sir Charles Bell on their side. But while his

work was still a new thing, he spoke in another way of it:--

"I found that injury done to the anterior portion of the spinal

marrow convulsed the animal more certainly than injury to the

posterior portion; but I found it difficult to make the

experiment without injuring both portions.

"Next, considering that the spinal nerves have a double root,

and being of opinion that the properties of the nerves are

derived from their connections with the parts of the brain, _I

thought that I had an opportunity of putting my opinion to the

test of experiment, and of proving at the same time_ that nerves

of different endowments were in the same cord (nerve-trunk) and

held together by the same sheath.

"On laying bare the roots of the spinal nerves, I found that I

could cut across the posterior fasciculus of nerves, which took

its origin from the posterior portion of the spinal marrow,

without convulsing the muscles of the back; but that on touching

the anterior fasciculus with the point of the knife, the muscles

of the back were immediately convulsed.

"_Such were my reasons for concluding_ that the cerebrum and

cerebellum were parts distinct in function, and that every nerve

possessing a double function obtained that by having a double

root. _I now saw the meaning_ of the double connection of the

nerves with the spinal marrow; and also the cause of that

seeming intricacy in the connections of nerves throughout their

course, which were not double at their origins."

It is impossible to reconcile the 1830 sentences with this vivid

personal account of himself; _I had an opportunity of putting my

opinion to the test of experiment ... an opportunity of proving ...

Such were my reasons for concluding ... I now saw...._ It is just what

all men of science say of their experiments: the very phrase of

Archimedes, and Asellius, and de Graaf. If Sir Charles Bell had been

working at the facts of chemistry or of botany, who would have doubted

the meaning of these words?

This same inconsistency of sentences occurs elsewhere in his _Nervous

System of the Human Body_. In one place he says that he has made few

experiments: _They have been simple, and easily performed, and I hope

are decisive._ In another he says: "_After making several experiments

on the cerebrum and cerebellum, I laid the question of their functions

entirely aside_, and confined myself to the investigation of the

spinal marrow and the nerves; _a subject which I found more within my

power_, and which forms the substance of the present volume."

Next, take his account of the cranial nerves:--

"It was necessary to know, in the first place, whether the

phenomena exhibited on injuring the separate roots corresponded

with what was suggested by their anatomy....

"Here a difficulty arose. An opinion prevailed that ganglions

were intended to cut off sensation; and every one of these

nerves, which I supposed were the instruments of sensation, have

ganglions on their roots. Some very decided experiment was

necessary to overturn this dogma. (Account of the experiment.)

By pursuing the inquiry, it was found that a ganglionic nerve is

the sole organ of sensation in the head and face: ganglions were

therefore no hindrance to sensation; and thus my opinion was

confirmed.... _It now became obvious_ why the third, sixth, and

ninth nerves of the encephalon were single nerves in their

roots....

"Observing that there was a portion of the fifth nerve which did

not enter the ganglion of that nerve, and being assured of the

fact by the concurring testimony of anatomists, I conceived that

the fifth nerve was in fact the uppermost nerve of the spine....

This opinion was confirmed by experiment.... (Account of an

experiment on the dead body.) On dividing the root of the nerve

in a living animal, the jaw fell relaxed. Thus its functions are

no longer matter of doubt: it is at once a muscular nerve and a

nerve of sensibility. And thus the opinion is confirmed, that

the fifth nerve is to the head what the spinal nerves are to the

other parts of the body, in respect to sensation and volition."

The value of the experimental method could hardly be stated in more

emphatic words. He supposed something, conceived it, had an opinion

about it. Anatomy had suggested something to him. He put his opinion

to the test of phenomena, that is to say, to the test of visible

facts; and then his opinion was confirmed. As with the spinal

nerve-roots, so with the fifth cranial nerve--his work was successful,

because he followed the way of experiment.

He was by nature of a most complex and sensitive temperament, full of

contrary forces--one man in 1811, another in 1830. In 1811 he wrote,

_I now saw the meaning of the double connection of the nerves_; in

1830 he had come to hate the _stupid sterile materialism_ of the

French school: he beheld anatomy falling behind physiology, and his

Windmill Street school perishing to make way for the Hospital schools

and for the University of London. He was before everything else a

great anatomist: he stood up for the honour of anatomy against the new

physiology, and for the honour of the Monroes and the Hunters against

Magendie: he hated the notion that any man should proceed to

experiments on function till the very last secrets had been got out of

structure. He died a few years afterward. The 1830 writings are his

last stand for the defence of his country, his school, and his beloved

anatomy, against the methods of Magendie; who said of himself, "I am a

mere street scavenger, _chiffonier_, of science. With my hook in my

hand and my basket on my back, I go about the streets of science,

collecting what I find."

This open conflict between Bell's first and last thoughts is a part of

his character: he was brilliant, impulsive, changeable, inconsistent;

and, what is more important, his honour kept him from trying to evade

this trumpery charge of inconsistency; and he reprinted the 1811

Preface in the book that he published in 1830. Doubtless he would have

picked his words more carefully if he had foreseen that one of the

1830 sentences would be wrested out of its place in his life's work,

and used as false evidence against the very method that he followed.

His observations on the cranial nerves brought about an immediate

change in the practice of surgery:--

"Up to the time that Sir Charles Bell made his experiments on

the nerves of the face, it was the common custom of surgeons to

divide the facial nerve for the relief of neuralgia, _tic

douleureux_; whereas it exercises, and was proved by Sir Charles

Bell to exercise, no influence over sensation, and its division

consequently for the relief of pain was a useless operation."

(Sir J. Erichsen.)

The relation of Magendie's work on the nerve-roots to Bell's

work need not be considered here. The exact dates of Bell's

observations are given by one of his pupils in the Preface to

the 1830 volume. Magendie finally proved the sensory nature of

the posterior nerve-roots: "The exact and full proof which he

brought forward of the truth which Charles Bell had divined

rather than demonstrated, that the anterior and posterior roots

of spinal nerves have essentially different functions--a truth

which is the very foundation of the physiology of the nervous

system--is enough by itself to mark him as a great

physiologist." (Sir M. Foster, _loc. cit._)

2. _Marshall Hall_ (1790-1857)

Reflex action had been studied long before the time of Marshall Hall.

The Hon. Robert Boyle (1663) had observed the movements and actions of

decapitated vipers, flies, silkworms, and butterflies. Similar

observations were made on frogs, eels, and other lower animals, by

Redi, Woodward, Stuart, Le Gallois, and Sir Gilbert Blane. According

to Richet, it was Willis who first gave the name _reflex_ to these

movements.

It cannot be said that these first studies of reflex action did much

for physiology. But the following translation from Prochaska (1800)

shows how they cleared the way for Marshall Hall's work, by the proof

that they gave of the liberation of nervous energy in the spinal

cord:--

"These movements of animals after decapitation must needs be by

consent and commerce betwixt the spinal nerves. For a

decapitated frog, if it be pricked, not only draws away the part

that is pricked, but also creeps and jumps; which cannot happen

but by consent betwixt the sensory nerves and the motor nerves.

The seat of which consent must needs be in the spinal cord, the

only remaining portion of the sensorium. _And this reflexion of

sensory impressions into motor impressions is not accomplished

in obedience to physical laws alone--wherein the angle of

reflexion is equal to the angle of incidence, and reaction to

action--but it follows special laws as it were written by Nature

on the spinal cord, which we can know only by their effects, but

cannot fathom with the understanding._ But the general law,

whereby the sensorium reflects sensory impressions into motor

impressions, is the preservation of ourselves."

It was not possible, in 1800, to go further, or to put the facts of

reflex action more clearly: but this fine sentence gives no hint of

the truth that guided Marshall Hall--that the "consent and commerce"

of reflex action are to be found at definite points or levels in the

spinal cord; that the cord no more "works as a whole" than the brain.

The greatness of Marshall Hall's work lies in his recognition of the

divisional action of the cord: he proved the existence of definite

centres in it, he discovered the facts of spinal localisation, and

thus foreshadowed the discovery of cerebral localisation. In his

earlier writings (1823-33) he showed how the movements of the trunk

and of the limbs are only one sort of reflex action; how the larynx,

the pharynx, and the sphincter muscles, all act by the "consent and

commerce" of the spinal cord. Later, in 1837, he demonstrated the

course of nerve-impulses along the cord from one level to another, the

results of direct stimulation of the cord, and other facts of spinal

localisation. He noted the different effects of opium and of

strychnine on reflex action; and he extended the doctrines of reflex

action beyond physiology to the convulsive movements of the body in

certain diseases.

3. _Flourens_ (1794-1867)

Beside his work on the nervous system, Flourens studied the periosteal

growth of bone, and the action of chloroform;[7] but he is best known

by his experiments on the respiratory centre and the cerebellum. The

men who interpreted the nervous system followed the anatomical course

of that system: first the nerve-roots, then the cord, then the medulla

oblongata and the cerebellum, and last the cerebral hemispheres; a

steady upward advance, from the observation of decapitated insects to

the localisation of centres in the human brain. Flourens, by his work

on the medulla oblongata, localised the respiratory centre, the

nerve-cells for the reflex movements of respiration:--

"M. Flourens a circonscrit ce centre avec une scrupuleuse

précision, et lui a donné le nom de noeud vital" (Cl. Bernard.)

[7] When Flourens died, Claude Bernard was appointed to his place

in the French Academy; and, in the _Discours de Reception_ (May

27, 1869), said, "It is twenty-two years since the discovery of

anæsthesia by ether came to us from the New World, and spread

rapidly over Europe. M. Flourens was the first man who showed that

chloroform is more active than ether."

Afterward came the discovery of cardiac and other centres in the same

portion of the nervous system. Flourens also showed that the

cerebellum is concerned with the equilibration of the body, and with

the coordination of muscular movements; that an animal, a few days

old, deprived of sensation and consciousness by removal of the

cerebral hemispheres, was yet able to stand and move forward, but,

when the cerebellum was removed, its muscles lost all co-ordinate

action. (_Recherches Expérimentales_, Paris, 1842.) And from his work,

and the work of those who followed him, on the semicircular canals of

the internal ear, came the evidence that these minute structures are

the terminal organs of equilibration: that as the special senses have

their terminal apparatus and their central apparatus, so the

semicircular canals and the cerebellum are the terminal apparatus and

the central apparatus of the sense of equilibrium.

4. _Claude Bernard_ (1813-1878)

The discovery of the vaso-motor nerves, and of the control of the

nervous system over the calibre of the arteries, was made by Claude

Bernard at the outset of his work on the influence of the nervous

system on the temperature.[8] The evidence of Professor Sharpey before

the Royal Commission of 1875 shows how things had been misjudged,

before Bernard's time, in the light of "views taken from the Study of

Anatomy and Natural Motions":--

"I remember that Sir Charles Bell gave the increased size of the

vessels in blushing, and their fulness of blood, as an example

of the increased action of the arteries in driving on the blood.

It turns out to be just the reverse, inasmuch as it is owing to

a paralysis of the nerves governing the muscular coats of the

arteries."

[8] A full account of this discovery, and of its relation to the

experiments of Brown Séquard, Waller, and Budge, is given by Sir

Michael Foster in his life of Claude Bernard; and the question of

priority between Bernard and Brown Séquard need not be considered

here, for the experimental method was the only way open to either

of them. For an account of the work done, before Bernard, in this

field of physiology, see Prof. Stirling's admirable and learned

monograph, _Some Apostles of Physiology_ (Waterlow & Sons, London,

1902), p. 104.

Claude Bernard's first account of his work was communicated to the

Société de Biologie in December 1851. The following description is

taken from his _Leçons de Physiologie Opératoire_:--

"I will remind you how I was led to the discovery of the

vaso-motor nerves. Starting from the clinical observation, made

long ago, that in paralysed limbs you find at one time an

increase of cold, and at another an increase of heat, I thought

this contradiction might be explained by supposing that, side by

side with the general action of the nervous system, the

sympathetic nerve might have the function of presiding over the

production of heat; that is to say, that in the case where the

paralysed limb was chilled, I supposed the sympathetic nerve to

be paralysed, as well as the motor nerves; while in the

paralysed limbs that were not chilled, the sympathetic nerve had

retained its function, the systemic nerves alone having been

attacked.

"This was a theory, that is to say, an idea leading me to make

experiments; and for these experiments I must find a sympathetic

nerve-trunk of sufficient size, going to some organ that was

easy to observe, and must divide this trunk to see what would

happen to the heat-supply of the organ. You know that the

rabbit's ear, and the cervical sympathetic nerve of this animal,

offered us the required conditions. So I divided the nerve; and

immediately my experiment gave the lie direct to my theory--_Je

coupai donc ce filet et aussitôt l'expérience donna à mon

hypothèse le plus éclatant démenti_. I had thought that the

section of the nerve would suppress the function of nutrition,

of calorification, over which the sympathetic system had been

supposed to preside, and would cause the hollow of the ear to

become chilled; and here was just the opposite, a very warm ear,

with great dilatation of its vessels.

"I need not remind you how I made haste to abandon my first

theory, and gave myself to the study of this new state of

things. And you know that here was the starting-point of all my

researches into the vaso-motor and thermic system; and the study

of this subject is become one of the richest fields of

experimental physiology."

Waller, in 1853, studied the vaso-motor centre in the spinal cord; and

Schiff, in 1856, found evidence of the existence of two kinds of

vaso-motor nerves--those that constrict the vessels, and those that

dilate them. This view was finally established in 1858 by Claude

Bernard's experiments on the chorda tympani and the submaxillary

gland.

The _Leçons de Physiologie Opératoire_ were published in 1879. Twenty

years later, Sir Michael Foster says of Bernard's work:--

"It is almost impossible to exaggerate the importance of these

labours of Bernard on the vaso-motor nerves, since it is almost

impossible to exaggerate the influence which our knowledge of

the vaso-motor system, springing as it does from Bernard's

researches as from its fount and origin, has exerted, is

exerting, and in widening measure will continue to exert, on all

our physiological and pathological conceptions, on medical

practice, and on the conduct of human life. There is hardly a

physiological discussion of any width in which we do not sooner

or later come on vaso-motor questions. Whatever part of

physiology we touch, be it the work done by a muscle, be it the

various kinds of secretive labour, be it the insurance of the

brain's well-being in the midst of the hydrostatic vicissitudes

to which the changes of daily life subject it, be it that

maintenance of bodily temperature which is a condition of the

body's activity; in all these, as in many other things, we find

vaso-motor factors intervening. And if, passing the insecure and

wavering line which parts health from illness, we find ourselves

dealing with inflammation, or with fever, or with any of the

disordered physiological processes which constitute disease, we

shall find, whatever be the tissue specially affected by the

morbid conditions, that vaso-motor influences have to be taken

into account. The idea of vaso-motor action is woven as a

dominant thread into all the physiological and pathological

doctrines of to-day; attempt to draw out that thread, and all

that would be left would appear as a tangled heap."

5. _Cerebral Localisation_

Finally, moving upward along the anatomy of the nervous system,

physiology came to study the motor-centres and special sense-centres

of the cerebral hemispheres. The year 1861 may fairly be said to mark

the beginning of the discovery of these centres, when Broca, at a

meeting of the Anthropological Society of Paris, heard Aubertin's

paper on the connection between the frontal convolutions and the

faculty of speech. But, of course, some sort of belief in cerebral

localisation had been in the air long before Broca's time. Willis

(1621-1675), who was contemporary with Sir Isaac Newton, had written

of the brain as though its convolutions, or "cranklings" as he called

them, showed that its work was departmental:--

"As the animal spirits for the various acts of imagination and

memory ought to be moved within certain and distinct limits, or

bounded places, and these motions to be often iterated or

repeated through the same tracts or paths, for that reason these

manifold convolutions and infoldings of the brain are required

for these divers manners of ordinations of the animal

spirits--to wit, that in these cells or storehouses, severally

placed, might be kept the species of sensitive things, and as

occasion serves, may be taken from thence."[9]

[9] For an account of Willis' work on the nervous system, see Sir

Victor Horsley's _Fullerian Lectures_, 1891. Willis was the first,

or one of the first, to recognise the fact that the cerebral

ventricles are nothing more than lymph-cavities.

And Gall, a century after Willis, had collected and published, in

support of his system of phrenology, many cases and _post-mortem_

examinations showing the differentiation of the work of the brain.

Gall is a warning for all time against the dangers of deduction; he

had but one idea, and he drove it to death; but the clinical and

pathological facts which he amassed, in the hope of establishing a set

of doctrines out of all relation to facts, are as true now as ever;

and, if he had been content to go the way of induction, and to set

himself to the accumulation of facts, he might have become a great

physiologist. In his knowledge of the anatomy of the brain, and in the

dissection of the brain, he was far ahead of the men of his time; but

he followed his own imaginings, and left nothing that could last,

except those cases and pathological instances that are buried in the

ruins of his system. But there they are, and are still of value. For

example, Gall's case of loss of speech, after an injury involving the

speech-centres, ought to have commanded the attention of all

physiologists: but it came to nothing, because he used it to support

his doctrine of organs and bumps, and it shared the fate of that

doctrine. Phrenology is gone past recall; it died of that congenital

disease, the deductive fallacy; but there was a time when it might

have been turned to the service of science.

The excitement that Gall aroused by the spread of his ideas shows that

some belief in cerebral centres was waiting for development. All men

are by nature phrenologists; the commonplace excuses that are offered

for lapses of memory, venial offences, and inherited weaknesses, all

appeal to the comfortable notion that the offender is not wholly

perverted, and that some very small and strictly localised group of

cells is at fault. And it is probable that the physiology of the

central nervous system, with its present strong tendency toward

psychology, will some day be back, at a far higher level, above the

point where phrenology went wrong. As Mme. de Staël said, _L'esprit

humain fait progrès toujours, mais c'est progrès en spirale_. But the

question, whether the general desire for a rational system of

psychology will ever commend itself to physiology, belongs to the

future. All that is of present concern is the steady, continuous, and

successful advance, by the way of induction, and by the help of

experiments on animals, toward a clear and accurate statement of the

departmental work of the brain.

It is one of many instances how science and practice work together,

that the modern study of these centres began not in experiment but in

experience. The first centres that were thus studied were the

speech-centres; and the observation of them arose out of the cases

recorded by Bouillard in 1825, and Dax in 1836. Clinical observation,

and _post-mortem_ examination, found the speech-centres; physiological

experiments had nothing to do with it; and phrenology had, as it

were, found them, and then lost them. But at once, so soon as practice

gave the word to science, physiology set to work. These clinical facts

had been there all the time; loss of speech had gone with disease or

injury of "Broca's convolution" ever since man had been on the earth,

and nobody had seen the significance of this sequence. Then, after

1861, everything was changed; and in a few years physiology had mapped

out a large part of the surface of the brain, and had charted the

motor-centres.

The story of Broca's convolution is told in Hamilton's _Text-Book of

Pathology_:--

"In 1825, Bouillard collected a series of cases to show that the

faculty of speech resided in the frontal lobes. In the year 1836

M. Dax, in a paper read to the Medical Congress of Montpellier,

stated as a result of his researches that, where speech was lost

from cerebral causes, he believed the lesion was invariably

found in the left cerebral hemisphere, and that the accompanying

paralysis of the right side of the body is consequent upon this.

This paper for long lay buried in the annals of medical

literature, but was unearthed years afterwards by his son, and

presented to the French Academy. Bouillard's views were also

disinterred by Aubertin, and in the year 1861 were brought by

him before the notice of the Anthropological Society of Paris.

Broca, who was present at the meeting, had a patient under his

care at the time who had been aphasic (without power of speech)

for twenty-one years, and who was in an almost moribund state.

The autopsy proved of great interest, as it was found that the

lesion was confined to the left side of the brain, and to what

we now call the third frontal convolution. Broca was struck with

the coincidence; and when a similar case came under his care

afterwards, unaware of what had been done by Dax, he postulated

the conclusion that the integrity of the third frontal

convolution, and perhaps also part of the second, is essential

to speech. In a subsequent series of fifteen typical cases

examined, it was found that the lesion had destroyed, among

other parts, the posterior part of the third frontal in

fourteen. In the fifteenth case the destruction had taken place

in the island of Reil and the temporal lobe."

After 1861, physiology took the lead, and kept it. But, through all

the work, science and practice have been held together; the facts of

experimental physiology have been and are tested, every inch of the

way, by the facts of medicine, surgery, and pathology. The infinite

minuteness and complexity of the investigation, and its innumerable

side-issues, are past all telling. They who are doing the work, in

science and in practice, have always had in their thoughts the fear of

fallacies in the interpretation of these highest forms of life. Sir

William Gowers, fourteen years ago, wrote as follows of the earlier

workers:--

"Doubt was formerly entertained as to the existence of

differentiation of function in different parts of the cortex,

but recent researches have established the existence of a

differentiation which has almost revolutionised cerebral

physiology, and has vastly extended the range of cerebral

diagnosis. The first step of the new discovery was constituted

by the clinical and pathological observations of Hughlings

Jackson, which suggested the existence, on each side of the

fissure of Rolando, of special centres for the movements of the

leg, arm, and face. These observations led to the experiments of

Ferner, which resulted in the demonstration of the existence in

the cortex of the lower animals of well-defined regions,

stimulation of which caused separate movements, or evidence of

special sense excitation, while the destruction of the same

parts caused indications of a loss of the corresponding

function. Hence he came to the conclusion that these regions

constitute actual motor and sensory centres. Ferrier had,

however, been anticipated in many of these results by two German

experimenters, Fritsch and Hitzig, whose results, differing a

little in detail, correspond closely in their general

significance. Many other investigations of the same character

have since been made, of which those of Munk are especially

important. The original observations of Hughlings Jackson left

little doubt that the general facts, learned from experiments on

animals, are true of man; and this conclusion has been to a

large extent confirmed by pathological and clinical observations

directed to the verification on man of the pathological results.

To this verification the labours of Charcot and his coadjutors

have largely contributed. But the verification has already made

it probable that some differences exist between the brain of man

and that of higher animals (even of monkeys), and that the

conclusions from the latter cannot be simply transferred to the

former."

Many and great difficulties, beyond this danger of the fallacy of

"simple transference," beset every step of the work: it required the

right use of the most delicate and susceptible instruments and tests,

and the right understanding of anatomy, microscopic anatomy,

comparative anatomy, organic chemistry, electricity, and physics:

every moment of advance must be guarded, every word must be weighed.

Among the earlier difficulties, was the failure of almost all the

physiologists, before Hitzig, to produce muscular action by excitation

of the cerebral cortex. Longet, Magendie, Flourens, Matteuci, Van Deen,

Weber, Budge, and Schiff, had all failed. Hitzig (_Untersuchungen

über das Gehirn_, Berlin, 1874) had observed, in man, that it

was easy to produce movements of the eyes by the passage of the

constant current through the occipital region.[10] Taking this

fact for a starting-point, he used a very low current, and thereby

succeeded in producing certain definite muscular movements by

stimulation of the cortex in animals. Of Hitzig's work, Sir Victor

Horsley says:--

"It was not till 1870 that the next absolute proof (after Bell's

work in 1813) was obtained of the localisation of function, so

far as the highest centres of the nervous system were concerned.

In that year Fritsch and Hitzig discovered that electrical

excitation, with minimal stimuli, of various points of the

cortex, caused those storehouses, of which Willis spoke, to

discharge, and to reveal their function by the precise

limitation of the groups of muscles which they were able to

throw into action. These researches were abundantly confirmed

and greatly extended by Professor Ferrier, and thus has been

constructed in the history of this subject the most recent great

platform or stage of permanent advance."[11]

[10] That the surface of the brain is not sensitive of such

stimulation, that it does not perceive its own substance, was

known to Aristotle. The fact is so familiar that there is no need

to quote evidence of it, beyond that of Sir Charles Bell: "I have

had my finger deep in the anterior lobes of the brain, when the

patient, being at the time acutely sensible, and capable of

expressing himself, complained only of the integument."

[11] Horsley, _Fullerian Lectures_, 1891, _loc. cit._

The thirty years since Hitzig's work cannot be put here, for they

would take a volume to themselves. There have been differences of

interpretation of this or that fact, diversities of results, and

problems too hard to solve, and other difficulties, such as befall all

the natural sciences; but these imperfections amount to very little,

when the whole result comes to be reckoned. The marvel is that the

work is so nearly perfect, seeing its immeasurable complexity.

Let any man, who has but touched the study of physiology, consider

what is involved in even the most superficial observation of the

simplest facts of the nervous system: for instance, the ordinary

nerve-muscle preparation that is taught to every medical student, or

the microscopic structure of the spinal cord, or the Wallerian method.

Or let him consider how the physiology of the nervous system has been

founded on the lower forms of life: the work of Romanes and others on

the Medusa and the Echinodermata, and Huxley's work in biology, and

the endless chain of forces that are alike in man and in jelly-fishes.

Then let him try to estimate the output of hard thinking, for the

advance from lower to higher structures, and up to man; the vigilant

criticism of all theories and foregone conclusions, the incessant

self-judgment and wearisome doubts and disputes all the way,

elusiveness of facts, and vagueness of words. And the results thus

wrung out of science had still to be stated in terms of practice, and

tested by the facts of medicine, surgery, and pathology, and used in

every hospital in the civilised world, not only for the saving of

life, but also for the diagnosis and medical or surgical treatment of

innumerable varieties of disease or injury of the brain, the cord, or

the nerves. Sir Michael Foster, in a short summary of the problems of

physiology, puts clearly these consummate difficulties of the

physiology of the nervous system:--

"In the first place there are what may be called general

problems, such as, How the food, after its preparation and

elaboration into blood, is built up into the living substance of

the several tissues? How the living substance breaks down into

the dead waste? How the building up and breaking down differ in

the different tissues in such a way that energy is set free in

different modes, the muscular tissue contracting, the nervous

tissue thrilling with a nervous impulse, the secreting tissue

doing chemical work, and the like? To these general questions

the answers which we can at present give can hardly be called

answers at all.

"In the second place there are what may be called special

problems, such as, What are the various steps by which the blood

is kept replenished with food and oxygen, and kept free from an

accumulation of water; and how is the activity of the digestive,

respiratory, and excretory organs, which effect this, regulated

and adapted to the stress of circumstances? What are the details

of the vascular mechanism by which each and every tissue is for

ever bathed with fresh blood, and how is that working delicately

adapted to all the varied changes of the body? And, _compared

with which all other problems are insignificant and preparatory

only_, how do nervous impulses so flit to and fro within the

nervous system as to issue in the movements which make up what

we sometimes call the life of man?"

The physiology of the nervous system is wrought to finer issues now

than in the time of Bell and Magendie; and this generation of students

may live to see the present facts and methods of cerebral localisation

as the mere rudiments or elements of science. Happily for mankind,

science has already so far elucidated them that they have done good

service for the diagnosis and treatment of disease, and for the saving

of lives.

* * * * *

Some examples have been given, in the foregoing chapters, of the value

of physiological experiments on animals. It would be easy to lengthen

the list, for there is no general subject in all physiology that does

not owe something to this method: as Mr. Darwin said, in his evidence

before the Royal Commission of 1875, "I am fully convinced that

physiology can progress only by the aid of experiments on living

animals. I cannot think of any one step which has been made in

physiology without that aid." Many examples have been left out

altogether--the work of Boyle, Hunter, Lavoisier, Haldane, Despretz,

and Regnault, on animal heat and on respiration; of Petit, Dupuy,

Breschet, and Reid, on the sympathetic system; of Galvani, Volta,

Haller, du Bois-Reymond, and Pflüger, on muscular contractility:

nothing has been said of the work lately done on the suprarenal glands

and "adrenalin," and on the blood-pressure in its relation to

secretion. For the most part, only those examples have been taken that

occur far back in the history of physiology: more has been said about

the past than about the present. First, because it was necessary to

put an end to the false statements that are made, by those who are

opposed to all experiments on animals, about the work done in the

past. Next, because the abstruse details of physiology, in the

present, are not intelligible for general reading. Next, because it is

impossible now to isolate physiology, or to say what belongs to

physiology alone, to have back the simpler problems of the past, to

discover the circulation of the blood twice. But the experimental

method, alike in the past and in the present, has been the chief way

of advance. And if a forecast may be made without offence, it is

certain that the work of physiology, as in the past and the present,

so in the near future, will exercise a profound influence for good on

medical and surgical treatment. Among the subjects that especially

occupy physiologists now are, the more exact localisation and

interpretation of the special sense-centres, and the better knowledge

of the internal secretions and chemical influences of the glands and

tissues of the body. It would be hard to find two fields of work more

sure to favour the growth of the _arbor vitæ_ side by side with the

_arbor scientiæ_.

But the last word here must be said by a physiologist of the very

highest authority, Professor Starling. He has kindly given me, for

this edition, the following note:--

"Among the researches of the last thirty years, those bearing on

the _Circulation of the Blood_ must take an important place,

both for their physiological interest and for the weighty

influence they have exerted on our knowledge and treatment of

disorders of the vascular system, such as heart disease. We have

learned to measure accurately the work done by the great

heart-pump; and by studying the manner in which this work is

affected by different conditions, we are enabled to increase or

diminish it, according to the needs of the organ. Experiments in

what is often regarded as the most transcendental department of

physiology--_i.e._ that which treats of muscle and nerve--have

thrown light on the wonderful process of 'compensation,' by

which a diseased heart is able to keep up a normal circulation.

"_Vaso-motor System._--Largely by the labours of British

physiologists, the exquisite control exercised by the nervous

system over every blood-vessel in the body has been brought to

light, the paths tracked out, and the mechanisms elucidated, by

means of which the circulation through each part of the body is

subordinated to the needs of the whole. Since the chief

vaso-motor nerves take their course through the sympathetic

system, the researches on their distribution have led to the

mapping out of the whole of this system, and to an accurate

knowledge of its functions. We are now acquainted with the

course, to all parts of the body, of the nerves which not only

determine the changes in the calibre of the blood-vessels, but

affect also the secretion of sweat and the erection of the

hairs. Incidentally, the mapping out of these nerves, in the

hands of Mackenzie, Head, and others, has led to more power of

localising the seat of visceral disease.

"_Digestion._--Our knowledge of the processes of digestion has

of late years received a great accession by the work of

Professor Pawlow, of St. Petersburg. His success is largely due

to his recognition of the importance of keeping his experimental

animals under the most normal conditions possible, and of

studying the different parts of the alimentary tract in animals

which were not anæsthetised, but which were free from any pain

or even discomfort, either of which conditions materially

interferes with the activity of the digestive glands. He

therefore established in dogs fistulæ in chosen portions of the

alimentary canal, analogous to the fistula which accident

rendered so valuable in the case of Alexis St. Martin. Not only

has the knowledge thus gained enabled the physician to

understand the sequel of events in disordered digestion, but the

success of the operative measures undertaken by physiologists

for the elucidation of their science has emboldened surgeons to

attack disease in the most various parts of the alimentary

canal.

"Renewed study of the secretion of pancreatic juice evoked by

the passage of the acid digestive products from the stomach into

the small intestine, which had been described by Pawlow, has

resulted in the discovery of a new class of chemical agents,

which act as special messengers from one part of the body to

another, and exercise an important function in determining the

action of all parts to one common end.

"_Respiration._--The investigation of the chemical properties of

the colouring matter of blood, and of its compound with carbon

monoxide, has resulted, in the hands of Dr. Haldane, in the

laying down of measures for the prevention of accidents from

choke-damp or after-damp in mines. The same investigation has

resulted in the discovery of a method of determining the total

amount of blood circulating in the body of a living man. The

application of this method has already added largely to our

knowledge of the pathology of different forms of anæmia, as well

as of the conditions obtaining in heart disease. Experiments by

Hill and others on the physiological effects of compressed air

have shown the precautions which should be observed in all

diving operations. A proper appreciation of these results by

diving-engineers would not only entirely obviate the cases of

'caisson disease,' but would enable diving to be carried on

safely to a greater depth than has hitherto been attempted.

"It is impossible, however, to enumerate all the physiological

gains of the last twenty or thirty years, or to point out their

manifold applications in the cure and prevention of disease. The

full control of the processes of disease, which is the goal of

the physician and the surgeon, can only be attained through an

accurate knowledge of the conditions governing the functions of

the healthy body. The foundation of medicine and surgery is

physiology: and it is only on living animals that the processes

of life can be investigated."