"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.)
"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.)
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 namereflexto 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 thelimbs 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.
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 nœud vital" (Cl. Bernard.)
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.
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 hadbeen 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."
Claude Bernard's first account of his work was communicated to the Société de Biologie in December 1851. The following description is taken from hisLeçons 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 mytheory—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."
"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 mytheory—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.
TheLeçons de Physiologie Opératoirewere 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 bya 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."
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 anddistinct 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]
And Gall, a century after Willis, had collected and published, in support of his system of phrenology, many cases andpost-mortemexaminations 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 gonepast 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, andpost-mortemexamination, found the speech-centres; physiological experiments had nothing to do with it; and phrenology had, asit 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'sText-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 thirdfrontal 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 theconstant 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]
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 freein 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?"
"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 freein 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. Darwinsaid, 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 specialsense-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 thearbor vitæside by side with thearbor 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 theCirculation of the Bloodmust 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 orafter-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."
"Among the researches of the last thirty years, those bearing on theCirculation of the Bloodmust 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 orafter-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."
Pathology, the study of the causes and products of diseases, is a younger science than physiology: the use of the microscope was the beginning of pathology; and the microscope, even so late as sixty years ago, was very different to the microscope now. The great pathologists of that time had not the lenses, microtomes, and reagents that are now in daily employment; they knew nothing of the present methods of section-cutting and differential staining. But the publication in 1839 of Schwann's cell-theory marks the rise of modern pathology. In 1843, Darwin wrote his first draft of the doctrine of the origin of species; and Pasteur, that year, was in for his examination at the École Normale. The work of Schwann, Virchow, and Pasteur had such profound influences on science that the span of sixty years seems to cover the modern development of pathology: and this span of years is marked, half-way, by the rise of bacteriology. In 1875, when the Royal Commission on Experiments on Animals was held in London, the evidence was concerned practically with physiology alone: very little was said about pathology, and of bacteriology hardly a word. The witnesses say that they "believe they are beginning to get an idea" of the true nature oftubercle: and the evidence as to the nature of anthrax, given by Sir John Simon, reads now like a very old prophecy:—
"We are going through a progressive work that has many stages, and are now getting more precise knowledge of the contagium. By these experiments on sheep it has been made quite clear that the contagium of sheep-pox issomething of which the habits can be studied: as the habits of a fern or a moss can be studied: and we look forward to opportunities of thus studying the contagium outside the body which it infects. This is not a thing to be done in a day, or perhaps in ten years, but must extend over a long period of time.Dr. Klein's present paper represents one very important stage of a vast special study. He gives the identification of the contagium assomething which he has studied to the end in the infected body, and which can now in a future stage be studied outside the body."
Thirty years ago, there was no bacteriology, in the present sense of the word: and now the "habits" of these "contagia" have been studied, outside and inside the body, with amazing accuracy. It has been proved, past all possibility of doubt, that the pathogenic bacteria are the cause of infective diseases; they have fulfilled Koch's postulates—that they should be found in the diseased tissues, be cultivated outside the body, reproduce the same disease in animals, and be found again in the tissues of those animals. By an immeasurable amount of hard work crowded into a few years, this New World of bacteriology has been subdued. The Royal Commissioners of 1875, speaking of physiological experiments only, said, "It would require a voluminous treatise to exhibit in a consecutive statement the benefits that medicine and surgeryhave derived from these discoveries." If physiology in 1875 required a treatise, bacteriology in 1906 requires a library: and it is impossible here to give more than the faintest outline of some of the work that has been done.
But all pathology is not bacteriology; and it would take a treatise of prodigious length to set forth the work of modern pathology in the years before anything was known of bacteria. The microscopic structure of tumours and of all forms of malignant disease, the nature of amyloid, fatty, and other degenerative changes, and the chief facts of general pathology—hypertrophy and atrophy, necrosis, gangrene, embolism, and many more—all these subjects were studied to good purpose, before bacteriology. Above all, men were occupied in the study of inflammation under the microscope. It was this use of the microscope that revolutionised pathology; especially, it made visible the whole process of inflammation, the most minute changes in the affected tissues, the slowing and arrest of the blood in the capillaries, the choking-up of the stream, and the escape of blood-cells out of the capillaries into the tissues. Everything had been made ready for the fuller interpretation that was coming from bacteriology: the old naked-eye descriptions of inflammation were left behind; men set aside the definition of Celsus, that it wasrubor et tumor cum colore et dolore—words that sound like Molière's jest about thevis dormitivaof opium—they watched inflammation under the microscope, in such transparent structures as the frog's web and mesentery, the bat's wing, and the tadpole's tail. It was thus that Wharton Jones discovered the rhythmical contraction of the veins in the bat's wing. The discovery of the escapeof the white blood-cells,diapedesis, through the walls of the capillaries, was made by Waller and Cohnheim. To those who are opposed to all experiments on animals, it may seem a very small thing that a blood-cell should be on one side or the other of a microscopic film in a tadpole's tail; but thisdiapedesis, the first move of the blood in its fight against disease, is now seen, in the light of Metschnikoff's work, as a fact of very great importance.
The history of this transitional period, from the study of inflammation in transparent living tissues to the use, in surgery, of the facts of bacteriology, is told in Lord Lister's Huxley Lecture, October 1900. He describes how the foundations were laid in surgical pathology, by microscopical and experimental work on inflammation, coagulation, suppuration, and pyæmia, for bacteriology to build on: how his own share of the work began when he was house-surgeon to Sir John Erichsen at University College Hospital, and afterward to Mr. Syme in Edinburgh, and how it was continued through all his Edinburgh and Glasgow life:—
"After being appointed to the Chair of Surgery in the University of Glasgow, I became one of the surgeons to the Royal Infirmary of that city. Here I had, too, ample opportunities for studying hospital diseases, of which the most fearful was pyæmia. About this time I saw the opinion expressed by a high authority in pathology that the pus in a pyæmic vein was probably a collection of leucocytes. Facts such as those which I mentioned as having aroused my interest in my student days in a case of pyæmia, made such a view to me incredible; and I determined to ascertain, if possible, the real state of things by experiment...."While these investigations into the nature of pyæmia were proceeding, I was doing my utmost against thatdeadly scourge. Professor Polli, of Milan, having recommended the internal administration of sulphite of potash on account of its antiputrescent properties, I gave that drug a very full trial as a prophylactic.... At the same time, I did my best, by local measures, to diminish the risk of communicating contagion from one wound to another. I freely employed antiseptic washes, and I had on the tables of my wards piles of clean towels to be used for drying my hands and those of my assistants after washing them, as I insisted should invariably be done in passing from one dressing to another. But all my efforts proved abortive; as I could hardly wonder when I believed, with chemists generally, that putrefaction was caused by the oxygen of the air."It will thus be seen that I was prepared to welcome Pasteur's demonstration that putrefaction, like other true fermentations, is caused by microbes growing in the putrescible substance. Thus was presented a new problem: not to exclude oxygen from the wounds, which was impossible, but to protect them from the living causes of decomposition by means which should act with as little disturbance of the tissues as is consistent with the attainment of the essential object.... To apply that principle, so as to ensure the greatest safety with the least attendant disadvantage, has been my chief life-work."[12]
"After being appointed to the Chair of Surgery in the University of Glasgow, I became one of the surgeons to the Royal Infirmary of that city. Here I had, too, ample opportunities for studying hospital diseases, of which the most fearful was pyæmia. About this time I saw the opinion expressed by a high authority in pathology that the pus in a pyæmic vein was probably a collection of leucocytes. Facts such as those which I mentioned as having aroused my interest in my student days in a case of pyæmia, made such a view to me incredible; and I determined to ascertain, if possible, the real state of things by experiment....
"While these investigations into the nature of pyæmia were proceeding, I was doing my utmost against thatdeadly scourge. Professor Polli, of Milan, having recommended the internal administration of sulphite of potash on account of its antiputrescent properties, I gave that drug a very full trial as a prophylactic.... At the same time, I did my best, by local measures, to diminish the risk of communicating contagion from one wound to another. I freely employed antiseptic washes, and I had on the tables of my wards piles of clean towels to be used for drying my hands and those of my assistants after washing them, as I insisted should invariably be done in passing from one dressing to another. But all my efforts proved abortive; as I could hardly wonder when I believed, with chemists generally, that putrefaction was caused by the oxygen of the air.
"It will thus be seen that I was prepared to welcome Pasteur's demonstration that putrefaction, like other true fermentations, is caused by microbes growing in the putrescible substance. Thus was presented a new problem: not to exclude oxygen from the wounds, which was impossible, but to protect them from the living causes of decomposition by means which should act with as little disturbance of the tissues as is consistent with the attainment of the essential object.... To apply that principle, so as to ensure the greatest safety with the least attendant disadvantage, has been my chief life-work."[12]
And, of course, the application of that principle is not limited to the performance of the major operations of surgery. It is in daily use in every hospital, and in every practice all the world over, for the safe and quick healing of whole legions of injuries, "casualties," and minor operations.
But what of Semmelweis, and his study of puerperal fever? Did he not, before Lord Lister, and without the help of experiments on animals, discover antisepticsurgery? His claim is urged by those who are opposed to all such experiments. And the answer is, that his work was lost just for want of experiments on animals. If he could have demonstrated, as Pasteur did, the living organism, the thing itself, there in the tissues of an infected rabbit, and in a test-tube, and under a microscope, he might have stopped the mouths of his adversaries. He could not. He could only demonstrate to them the fact that their patients died, and his patients lived: and that some sort of direct infection was the cause of the deaths. The tragedy of his life cannot be told too often, and may be told again here.[13]For want of the final proof that bacteriology, and the inoculation of animals, alone could give, he was unable to hold out against his enemies till Pasteur could rescue him.
In 1846, when he was twenty-three years old, Ignaz Semmelweis was appointed assistant-professor in the maternity department of the huge general hospital of Vienna. For many years, the mortality in the lying-in wards had been about 1.25 per cent., and no more. Then, under a new professor, it had risen; and, for some years before Semmelweis came on the scene, it had been 5 per cent., or even 7 per cent. In October 1841, there had been an epidemic that had lasted till May 1843. In these twenty months, out of 5139 women delivered, 829 had died; that is to say, 16 per cent.
There were two sets of wards in the maternity department. The one set may be called Clinique A, and the other Clinique B. For many years, the mortality had been the same in each. In 1841 a change wasmade: Clinique A was assigned to the teaching of students, and Clinique B to the teaching of midwives: and, so soon as this change had been made, the mortality in Clinique B became less, but the mortality in Clinique A did not. Commissions of inquiry were held, and in vain. It was suggested that the foreign students were somehow to blame, nobody knew why; and many of them were sent away. Still the deaths went on. Women admitted to Clinique A would go down on their knees and pray to be allowed to go home; almost every day the bell was heard ringing in the wards, for the administration of the Sacrament to a dying woman. People talked about atmospheric influences, and overcrowding, and the tainted air of old wards, and the power of the mind over the body: and Semmelweis set to work.
He observed that cases of protracted labour in Clinique A died, almost all of them; but not in Clinique B. He observed also that cases of premature labour, nearly all of them, did well, whichever Clinique they were in; so did those women who were delivered before they came to the hospital, and were admitted after delivery. He observed also that a row of patients, lying side by side, would all be attacked at once in Clinique A; which never happened in Clinique B. He tried everything: he altered the details of treatment; he used various subterfuges to prevent one of the professors from examining serious cases; he enforced this or that rule in Clinique A, because it was the custom in Clinique B; he slaved away at the notes of the cases—and at last the truth came to him, by the death of one of his friends from a dissection-wound. He says, "My friend's fatal symptoms unveiled to my mind an identity with those which I had so often noticed at the deathbeds of puerperal cases." He saw now that thestudents, coming straight from the dissecting-rooms, had infected the patients during examination.
In May 1847 he gave orders that every student, before examining, should thoroughly disinfect his hands. But, though he had reckoned with dissecting-room poisons, he had forgotten to reckon with other sources of infection. In October of that year, a woman was admitted who had malignant disease; of twelve women examined after her, eleven got puerperal fever, and died. In November, a woman was admitted who had a suppurating knee-joint, with sinuses; and eight women were infected from her, and died. Therefore Semmelweis said, "Not only can the particles from dead bodies generate puerperal fever, but any decomposed material from the living body can also generate it, and so can air contaminated by such materials." Henceforth he isolated all infected cases, he enforced the strict use of disinfectants: and the mortality in Clinique A, which in May 1847 had stood at 12.24 per cent., fell in December to 3.04, and in 1848 was 1.27.
His work was taken up with enthusiasm by Hebra, Skoda, and Haller; the news of it was sent to every capital in Europe. In February 1849 Haller read a paper on it before the Medical Society of Vienna, and said, "The importance of these observations is above all calculation,both for the maternity department and for the hospitals in general, but particularly for the surgical wards." A committee was nominated to report on the whole matter; but it was opposed by the professor in charge of Clinique A, and nothing came of it. In May 1850, Semmelweis opened a great debate on puerperal fever, which occupied three sittings of the Vienna Medical Society. His opponents were there in full force, all the Scribes and Pharisees of the profession. They broughtabout a vague distrust of his figures and his facts; they got people to believe that there must be "something else" in puerperal fever, as well as the local infection. Semmelweis began to be discouraged. The University authorities made a dead set against him—they refused to renew his appointment, they got him out of the hospital, and out of Vienna. He went to Pesth, and was Professor of Midwifery there; but the same opposition and hostility were at Pesth as at Vienna. Slowly he began to lose his hold over himself, went down hill, became excitable and odd. The end came in July 1865. At a meeting of University professors, he suddenly took a paper from his pocket and read aloud to them a solemn oath, to be enforced on every midwife and every doctor. His mind had given way: he was moved to an asylum at Vienna, and died there a few weeks later. He was only forty-two when he died—What a wounded name, Things standing thus unknown, shall live behind me.
The contrast between the work of Semmelweis and the work of Pasteur cuts like a knife here. The failure of Semmelweis' teaching may be estimated by the fact that it had all to be done over again. The year of his success at Vienna was 1848. Eight years later, in the Paris Maternity Hospital, between 1st April and 10th May 1856, came such an outbreak of puerperal fever that out of 347 patients 64 died. In 1864, out of 1350 cases, 310 deaths. In Jan.-Feb. 1866, out of 103 cases, 28 deaths: "Women of the lower classes looked upon the Maternité as the vestibule of death." In 1877-78, came the use of carbolic acid and perchloride of mercury at the hospital, thirty years after Semmelweis' work: and, about the same time, Pasteur's discovery of the streptococcus in puerperal fever.[14]Pasteurcould demonstrate to his opponents the visible cause of the infection, the thing itself. Roux tells the story:—