An Introduction to the Study of Experimental Medicine

It was said of Claude Bernard, "He is not merely a physiologist, he is physiology." His IntToduction to the Study of Experimental Medicine, first published in 1865, has remained a classic, and, more than that, a classic which is still read. "Claude Bernard's Introduction to the Study oj Experimental Medicine, first published in 1865, is a classic of the philosophy of science. ... Its title may have misled readers into expecting a technical treatise on physiology; it is in fact an essay on method not unworthy to be classed with that of Descartes. We shall not find here the pretensions to system, arrangement, and thoroughness of more elaborate treatises on scientific method. Here everything is said directly, simply, without pretentiousness or pseudo-profundity; we can almost hear the harpsichord playing in the background. But there is nothing forced or contrived in this elegance; every page is informed with the judgment and educated memory of a superb experimenter. We seem to be always in the presence of a person, meditating upon a lifetime's experience of creative research." {Max Black, Professor of Philosophy at Cornell Uni rersity. )

The Introduction is more than a classic; it is a classic which is still read. It is io fact among the One Hundred Great Books which comprise the basic curriculum of St. John's College. For many readers the most interesting and valuable part of the Introduction will always be Bernard's descriptions of the successive steps of each of his principal discoveries and his consequent deduction of the way in which the mind of a scientist goes to work upon a problem.

Bernard is the founder of experimental medi cine, i.e., the artificial production of disease by means of chemical and physical manipulation. His research in physiology, which is the foundation of scientific medicine and the most inipor tant part of biology, has immortalized his name Said a foreign scientist, "Claude Bernard is not merely a physiologist, he is physiology." iN,i*T'TUTE OF MEURQLOGY, THS NATIOr4AL HSSFITAL. QUEEN SQUAim, The discoverer of natural knowledge stands apart in the modern woild, an obscure and slightly mysterious figure. By the abstract character of his researches his individuality is obliterated; by the rational form of his conclusions his method is concealed ; and at best he can be known only through an effort of the imagination. This is perhaps inevitable. But the unfortunate effects are enhanced by convention which to-day prescribes a formal, rigorous and impersonal style in the composition of scientific literature. Thus while it is no more difficult to know Galileo and Harvey than Cervantes and Milton through their writings, or to perceive their habits and methods of work, psychological criticism will often seek in vain the personality and the behavior of the person behind the modern scientific printed page. Yet whoever fails to understand the great investigator can never know what science really is.

Such knowledge is not taught in the schools. Even more than the scientific memoir, the treatise and the lecture are formal, logical, systematic; thus truly intelligible and living only to the initiated. As much as possible science is made to resemble the world which it describes, in that all vestiges of its fallible and imaginative human origin are removed. Since the publication of Euclid's immortal textbook this has been the universal and approved usage. Little doubt should remain that it is the best. But then the burden must fall upon the student of initiating himself into mysteries which no one will explain to him.

What he lacks is understanding of the art of research and of the inevitable conditions and limitations of scientific discovery, an understanding, in short, of the behavior of the man of genius, not a rationalized discussion of scientific method. The latter may be sought in many learned works and in the teachings of academic philosophers; a good account of the former is far to seek. It is, therefore, not the least of the merits of Claude Bernard's An Introduction to the Study of Experimental Medicine that we have here an honest and successful analysis of himself at work by one of the most intelli-

gent of modem scientists, a man of genius and a great physiologist. This work lays bare, sO' far as that is possible, what others have concealed. With due regard to such analysis and logical formulation as are indispensable for intelligibility of exposition, Claude Bernard has avoided a 'posteriori rationalization as he has a priori dogmatism. Thus it is possible to perceive his scientific method as the habit of the man. His life is spent in putting questions to nature. These questions are the measure of his originality. He cannot tell how they arise, but the experimental idea seems to him a presentiment of the nature of things. Such ideas are, at any rate, the only fertilizing factor in research ; without them scientific method is sterile, and great discoveries are those which have given rise to the most luminous ideas.

The experiment, accordingly, is always undertaken in view of a preconceived idea, but it matters not whether this idea is vague or clearly defined, for it is but the question, vague or otherwise, which he puts to nature. Now, when nature replies, he holds his peace, takes note of the answer, listens to the end and submits to the decision. In short, the experiment is always devised with the help of a working hypothesis; the resulting observation is always made without preconceived idea. Such habits are not too easily formed, for man is by nature proud and inclined to metaphysics, but the practice of experimentation will cure these faults.

Claude Bernard is at pains to point out that even so modest an abstract description of method does violence, for the sake of clearness, to the complexity of human behavior. Beyond this his method is the curt of experimentation, an art which rests upon a perfect and habitual familiarity with the objects that he studies and with the details of his experimental procedure. The chapters in which all this is developed are pervaded by a spirit of honesty, simplicity and modesty, the mark of a great investigator. It is not difficult while reading them to see the man at work, full of ideas, a marvelous observer, marking and taking note even of that for which he is not looking, always doubting, but serenely and without scepticism, guarding himself from his hypothesis and even from the unconfirmed observation, yet ever confident in the determinism of nature and therefore in the possibility of rational knowledge.

The subject of his investigations was physiology, in the broadest and in the most modern sense, physiology conceived as the predestined foundation of scientific medicine and as the most important part of biology. Thus his science was seen by Claude Bernard with clear but prophetic vision, for he lived almost a half century before his time. He perceived that physiology rests securely upon the physicochemical sciences, because all that these sciences bring to light is true of organic as of inorganic phenomena. Also there is nothing but the difficulty of the task to hinder the reduction of physiological processes to physical and chemical phenomena. And yet this cannot be the last word, for physiology is more than bio-physics and biochemistry, biology more than applied physical science. He has himself, elsewhere, put the case as follows:

"Admitting that vital phenomena rest upon physico-chemical activities, which is the truth, the essence of the problem is' not thereby cleared up ; for it is no chance encounter of physico-chemical phenomena which constructs each being according to a pre-existing plan, and produces the admirable subordination and the harmonious concert of organic activity. "There is an arrangement in the living being, a kind of regulated activity, which must never be neglected, because it is in truth the most striking characteristic of living beings. . . .

"Vital phenomena possess indeed their rigorously determined physico-chemical conditions, but, at the same time, they subordinate themselves and succeed one another in a pattern and according to a law which pre-exist; they repeat themselves with order, regularity, constancy, and they harmonize in such manner as to bring about the organization and growth of the individual, animal or plant. "It is as if there existed a pre-established design of each organism and of each organ such that, though considered separately, each physiological process is dependent upon the general forces of nature, yet taken in relation with the other physiological processes, it reveals a special bond and seems directed by some invisible guide in the path which it follows and toward the position which it occupies.

"The simplest reflection reveals a primary quality, a quid proprium of the living being, in this pre-established organic harmony." * * Legons sur les Phenomenes de la Vie Commune aux Animaiix et aux VegitaiLX. Paris, 1878, Vol. 1, p. 50. I know of no other statement of the case since Aristotle's which seems to me to present so well a biologist's philosophy. It must not be expected, however, to find in the work of Claude Bernard a system of biological philosophy. He sets forth his views on the philosophy and the method of science, and they are really his views, the very convictions that he carries with him into the laboratory. But they are not a clear system of philosophy, nor a rational and logical scientific method, which neither he nor anyone else can believe in as he goes about his daily work. Hence, like everybody's real beliefs, they shade off into vague, more or less inconsistent, more or less doubtful opinions. This is reality itself.

The theory of organism is more than a philosophical generalization ; it is a part of the working equipment of the physiologist, fulfilling a purpose not unlike that of the second law of thermodynamics in the physical sciences. It has been more or less clearly understood and employed from the earliest times, and Claude Bernard did but perfect it. The theory of the constancy of the internal environment, a related theory, we ow^e almost wholly to Claude Bernard himself. There is no better illustration of his penetrating intelligence. A few scattered observations on the composition of blood sufiiced to justify, in his opinion, the assertion that the constancy of the internal environment {milieu interieur) is the condition of free and independent life.^ A large part of the physiological research of the last two decades may fairly be regarded as a verification and illustration of this theory, which, as Claude Bernard perceived, serves to interpret many of the most important physiological and pathological processes. It was this theory too that led him to a clear conception of general physiology, which he regarded as the fundamental biological science.

General physiology, according to him, includes the study of the physico-chemical properties of the environment of the cell, a similar study of the cell itself, beyond this of the physico-chemical relations between cell and environment, and, generally, of the phenomena common to animals and plants. This science, of which he is the founder, was destined to remain undeveloped until long after his death. To-day, with the aid of a physical chemistry unknown to the

* This should not be thought of as absolute constancy, and it should be understood that variations in the properties of the internal environment may be both cyclical and adaptive, that is functional, but in general may not be random and functionless. Claude Bernard's principle is the first approximation which suffices until the siibject has been broadly developed. contemporaries of Claude Bernard, it is fulfilling tbe promise which he alone could clearly see. He never had a more luminous presentiment of the nature of things than this vision of the future foundations of biology.

No man is a true prophet otherwise than through the possession of such intimate knowledge of a subject that he is able to say, "Thus matters must develop." Such was Claude Bernard's prophecy of the future of his own science. His understanding of physiology had become so perfect that the future could not be wholly doubtful. He knew where the path must lead, and it is this that makes his book so amazingly modern. In other respects he is only a highly intelligent man of the third quarter of the nineteenth century. Accordingly his treatment of some subjects, such as mathematics and physics, is a little old-fashioned, especially on the logical side. In general such defects are not only slight, but also unimportant from the medical standpoint. But his discussion of statistics could hardly be written to-day. There are indeed those, though few in number, who will agree with his criticisms. But, when he wrote, the influence of Galton had not been exerted and nobody realized that statistics afford a method, at once powerful, elegant and exact, of describing a class of objects as a class.

Physiology, as defined and understood in this book, with general physiology as its foundation, is the essential medical science. Medicine has passed through the empirical, the systematic, the nosological and the morphological stages and has entered upon the experimental stage. Thus it has finally become physiological, for physiology is the larger part of experimental medicine. Such is the principal thesis of the present work, which ought not to be obscured by the consideration of incidental topics, no matter how intrinsically important they may be.

This opinion, to be sure, does not yet meet with universal approval, and yet I believe that it has been at length fully confirmed by the experience of the twentieth century. Nevertheless, the confirmation was long delayed by the emergence of the bacteriological stage in the evolution of medicine. Unforeseen by Claude Bernard, this was the result of the discoveries of his contemporary, Pasteur. To-day, looking backward, we see how it was that bacteriological researches for a long time took the first place which Claude Bernard believed to be already assured to those of his own science. When

Pasteur began the study of micro-organisms a great gap existed in our knowledge of the organic cycle and of natural history. His work and that of his successors filled this gap, completed our present theory of the cycle of life and established the natural history of infectious diseases, of fermentations and of the soil. This was perhaps the most rapid advance of descriptive knowledge in the history of science. For the moment the researches of physiologists were overshadowed and the work of the young men diverted into the new fields. In time bacteriology grew into a fully developed science, perfected its methods, exploited its domain, and then, the most pressing work well done, resigned its leadership of the medical sciences.

Meanwhile a profound influence was exerted on what Professor Whitehead has called the intellectual climate. Claude Bernard's outlook may be described as biological and philosophical, and such a point of view seems necessary for the understanding of the deeper problems of medicine. Pasteur, however, always retained the chemist's outlook, and in him the will was more important than the reflective intellect. His successors have taken a position hardly more biological and, probably of necessity, have had little interest in rational theory. Such a climate is unfavorable to the growth of experimental medicine and especially of general physiology, for both are biological and rational.

This had been vaguely understood as early as the times of Galileo, of Borelli, and of Malpighi, when the minds of men were still fresh and not yet enslaved by specialism. But even Claude Bernard, because he still lacked the aid of modern physical chemistry, hardly appreciated the possibilities, very limited but very important, of the applications of the fully developed method of rational physical science, when guided and duly restrained by the judgment of a true physiologist, in the study of the ultimate phenomena of life.

In default of the physico-chemical foundations, during a period when bacteriology was the dominant influence in medical science, and next to it, perhaps, the highly specialized science of organic chemistry, when the prevailing activity was somewhat unintellectual, physiology continued in the old paths. Not until after the turn of the century did the movement which Claude Bernard had foreseen make itself felt. To-day it is well established and should be generally recognized. The result has already been a remarkable increase of experimental investigation and of rational theorizing in the clinic.

For the first time mathematics, physics, chemistry and physical chemistry, as aids to physiology, have passed into the hospitals. I believe that, for the reasons which Claude Bernard has explained, this will long remain the way of medical progress and that we have now definitely entered upon the epoch of experimental medicine. All progress entails evils and few experimenters can understand as Claude Bernard did the phenomena of life and the philosophy of the organism. For these reasons, and for others not so good, the growth of experimental medicine gives rise to criticism, as it did a half century ago. Experienced physicians, practised in the art of medicine and rightly believing that medicine is still and must always be an art, but also uncomfortable and suspicious through ignorance of the new development, are not lacking to unite with this opposition. So far as grounds for complaint exist they are due to the absence of that high intelligence and skill of the experimenter which are necessary to understand and to solve the complex problems of physiology. Here one can only plead the palliating circumstance that all human endeavor suffers from the same weaknesses. On the other hand, prevailing criticism of scientific medicine itself, no less than the earlier criticism of the nineteenth century, finds conclusive answer in this book.

Medicine is but a part of human biology and the study of human inheritance, constitution, intelligence and behavior, of adaptation to new conditions of life, and of a host of other subjects, far transcends the boundaries of medicine. But everywhere throughout this vast field physiology has the same importance as in the narrower field of medicine. Thus the Introduction may serve as a guide not only for those who are beginning the study of medicine, but for many others as well.

The sciences are not equal, nor do they preserve their rank unchanged as civilization moves on. During nearly a quarter of a millennium mechanics led all the others in intellectual interest and in influence upon European civilization. It will seem to many not too bold a prophecy, for the reasons that Claude Bernard has set forth, to look forward to a century in which physiology shall take a similar place. I venture to believe that that position will be reached when the experimental method has made possible a rational science of organism.

talized his name, but the present work and his other general writings have hardly attracted the attention which they deserve or exerted the influence of which they are capable. This is probably due both to the conflicting influence of bacteriology, organic chemistry and other sciences and, not less, to his own clearness of vision. That which he saw as the future of physiology remained for many decades hidden from others and so his writings were only half understood. Even general physiology is still hardly aware of the program which he set forth and which it has been unwittingly carrying out. There is, however, one well known instance of his influence exerted farther afield. As the idea of Balzac's Comedie Humaine was suggested by the biology of the early nineteenth century, so the naturalism of Zola was suggested by the works of Claude Bernard. Perhaps the result will not be thought worthy of the cause. Yet the instance is significant of the wide bearing of an interpretation of life which may be seen to be peculiarly well suited to the present conditions of the political and social as well as of the natural sciences.

Among great men, Claude Bernard should be counted fortunate in that he has not become a mythical figure. Unlike Pasteur, whose discoveries are hardly more remarkable, though their immediate influence has been immeasurably greater, and whose horizon was incontestably less broad, he remains a plain man, highly distinguished no doubt, but not obscured by the growth of a legend. It is possible not only to see him at work, but even to discover his purposes and his feelings. The desire to relieve suffering and a sense of duty are clearly apparent, and one may read between the lines the enduring satisfaction that he felt in the society of younger men who owed to him more than they could ever repay. But weightier still are the contentment which comes from work well done, the sense of the value of science for its own sake, insatiable curiosity and, above all, the pleasure of masterly performance and of the chase. These are the effective forces which move the scientist. The first condition for the progress of science is to bring them into play.

Claude Bernaed, born July 12, 1813, at Saint Jnlien near Villefranche,^ came to Paris in 1832, with almost no paraphernalia except a tragedy which had never been acted, and a farce-comedy which had had some success at a small theatre in Lyons. He showed these first attempts to Saint-Marc Girardin who was temporarily taking Guizot's place at the Sorbonne. Girardin advised him to learn a profession to live by, and to write poetry in his spare time : certainly he had no idea that standing before him was a future colleague in the French Academy. Young Claude Berna,rd followed this sensible advice and entered the school of medicine.

Though he received his appointment as hospital interne in 1839, he was anything but a brilliant pupil. His comrades did not suspect what lay hidden behind the huge forehead of this silent student who paid so little attention to his professors' teaching, that they easily condemned his meditative calm as mere laziness. Survivors remember and often describe that revelation, his publications on gastric sugar, the chorda tympani, the pneumogastric nerve and the spinal nerve, which suddenly revealed to the scientific world a sagacious and ingenious experimenter of rare operative skill.

Magendie's teaching brought this revolution about. As soon as Claude Bernard set foot in the laboratory of the College de France, his path was marked out. The celebrated physiologist's daring though somewhat disorderly experimentation, his pitiless criticism, the scepticism that included even his own discoveries, made a deep and, so to speak, creative impression on the young man's mind. But the pupil was so much more powerful than his master that he took from his teaching only its virtues of independence, and succeeded in keeping doubt within scientific bounds. To deep disdain for plausible explanations in which alluring chimeras are concealed, he easily added respect for the facts gathered in tradition, sincere belief when face to face with the unexpected which is often pregnant with discovery, respect for searching hypotheses and coordinating theories, * Department of the Rhone.