An Introduction to the Study of Experimental Medicine

without ever attributing to them independent authority or power. Finally what distinguished him especially from Magendie, and gave him his wholly individual character, was love of certainty, — that deep feeling for law, that immovable confidence that, — if the conditions in which vital phenomena come to pass are infinitely many, complex and hard to grasp, assemble and master experimentally, — they are none the less surely and fixedly linked to phenomena without any possibility of a quid divinum being invoked to explain the seemingly spontaneous irregularities which they present.

This is the main point where Claude Bernard showed his superiority, from the first moments of his scientific life. The pupil of Magendie, the sceptic, introduced determinism into the realm of physiology. Thanks to him, the scientific method, respect for whose laws leads to certainty in the sciences of dead matter, assumed equal authority in the sciences of living beings. Sciences are not of two kinds, the first proud and confident, the rest timid and hesitant ; the first sure of commanding and of being obeyed in experiments, the rest always in fear of an influence unknown in essence, force and goal.

It required no small effort to banish this menacing unknown from the field of physiology. The most celebrated of French physiologists, Bichat, had given it asylum, and everyone after him had thought it necessary to reckon with this capricious force, with these vital functions, whose role was to resist the universal laws of matter, which thus made all acts performed by living beings a series of miracles. Of course Magendie was not the man to let himself be frightened by this ghost; but he systematically and artificially simplified facts so that he only partly mastered them ; or else the multiplicity of conditions governing vital phenomena took away all his theoretical confidence in the result. Now, without results there can be no science. I must repeat that Claude Bernard, therefore, proved himself, almost from the outset, superior to both Magendie and Bichat, since he felt not only the endless multiplicity of unknown data in physiology, but also their subordination to the general laws of matter and their obedience to the experimental method.

Physiology could therefore extend its roots into the solid earth where its older sisters, physics and chemistry, are settled. The complexity of the problems made it essential, however, to set forth the rules of the experimental method in special formulae with a view to the intellectual and manual methods which are especially adapted to physiology. Through the whole first phase of his scientific life, Claude Bernard was haunted by this task. But the fascination of his laboratory and the hunt for discoveries so completely absorbed his time that he could demonstrate the experimental method only as Diogenes demonstrated motion.

And never was hunt for discoveries more fruitful. In twenty years, Claude Bernard found more dominating facts, not only than the few French physiologists working beside him, but than all the physiologists in the world. The activity of different glands and particularly of the pancreas, animal glycogenesis, experimental production of diabetes, the existence of the vasomotor nerves and the theory of animal heat, the influence of poisons, studied in themselves and as a means of analyzing physiological phenomena, the endless number of fresh facts, keen deductions and ingenious and suggestive insights, contained not only in his special memoirs but in the fourteen volumes, from his Lessons in Experimental Physiology Applied to Medicime (1885-1886) to his Lessons on Diabetes and Animal Glycogenesis (1877), in which he collected each year the results of his investigations and a summary of his courses, — these things gave him the position of a master unquestioningly accepted in France and abroad.

In official life he also attained the highest rank. In 1854, a chair of general physiology was founded for him at the Sorbonne, which in 1868 he surrendered, with beautiful magnanimity and grace, to his pupil, Paul Bert. In 1858 he took Magendie's place in the chair of medicine at the College de France. Member of the Academy of Sciences in 1854, he was called in 1868 to take Flourens' seat in the French Academy. Finally in 1869, by special decree, he entered the Senate; and he was almost the only member of that assembly whom no one ever thought of reproaching for a nomination which to him was so strange a surprise.

A few years before these unexpected literary and political honors thus sought him out in his laboratory, a serious event occurred in his life. A long and severe disease, during which he and his friends despaired of a favorable outcome, condemned him to physical inactivity. He had to leave his laboratory, and Paris too; he had to ask of his birthplace, once more and not in vain, the gift of life and health. Long months of isolation and rest gave back all his liberty

of mind. For the first time, lie had leisure for meditation and for setting in order, on paper, the results of his solitary reflections. A short preface, which was already in proof and which was to have preceded a sort of treatise on operative physiology which remains unfinished, grew, by successive additions, to the size of a pamphlet, then of a book which saw the light in 1865. The Introduction to the Study of Experimental Medicine struck cultivated minds with admiration and astonishment. Here physiologists were happy to find, reduced to precise formulse, set in order with marvellous art, and lighted by examples which themselves were like so many intellectual experiments, — here they were happy to find the rules of the experimental method, watching, seizing and, in spite of its struggles, mastering that organic Proteus of the deceitful metamorphoses. Men less taken up with professional difficulties were struck by the magnitude of the problems studied, by the clarity of exposition, the ease and good faith with which they were either solved or proved insoluble. Even the style attracted great attention ; its original flavor took even the French Academy's fancy : "You have created a style," said the severe Monsieur Patin, in his speech of welcome. And it was true. But how surprised the venerable critic would have been if he had read the earlier books in which Claude Bernard contented himself with enumerating his laboratory impressions in a narrative that is often scarcely well ordered. The eminent but naive master was never haunted by care for stage effect ; his style, whether spoken or written, is the equivalent of his ideas. In episodical narrative, he is often dragging and confused; but when a hard problem presents itself, when his thought is forced to fall back as if to conquer an obstacle or make a bound, then he concentrates, purifies and accentuates himself in definite formulas and often in verbal imagery.

As he was in his books, so was Claude Bernard in his courses and his conversation. His was not a docile thought, speaking every language and playing every role; and he never disciplined it to any conventions of profession or of social custom. If it escaped him, he followed it without rebellion, leaving his speech drooping, his lecture in confusion, while he listened to what it softly said to him. But if it grew interested in the immediate subject, then the professor or conversationalist, a moment ago so difficult and diffuse, awoke living, inventive, clear, eloquent, with surprising and sudden changes, and

always with both characteristics of true genius, ease and good faith. And no one possessed them in higher degree. That ease in raising himself to high summits, in acting in the midst of trying difficulties, especially struck readers of his admirable articles in the Revue des Deux Mondes. What the poet said of the goddess could be said of him : incesm patuit. After reading these articles, an eminent man said to me one day: "He does not make me merely think I understand, as you all do ; he makes me really understand.'' And in fact he did understand. Claude Bernard carried this ease from his physiological method into the philosophic realm. No one ever made discoveries more simply, more naively. To that first phase of hunting ideas, which consists, as Helvetius said, in seeing and starting the quarry, he brought a sureness of vision, an astounding penetration. Most scientific searchers are a kind of somnambulist who see only what they are looking for and what is on the track of their ideas;; their eyes are fixed on a point; and they fail to perceive not only what happens aside from that point, but even what appears there unforeseen. In one of his pupil's phrases, Claude Bernard seemed to have eyes all around his head. In the course of an experiment, students were stupefied when they saw him point out quite evident phenomena which no one but himself had seen. He discovered as others breathed.

With ease, good faith. That was his ruling characteristic. He never swerved from the deep sincerity of a man of science who must seek truth for its own sake and for the truths which follow from it, without concerning himself with the distant or indirect conclusions which lawyer-like men, with a cause to defend, try to draw from it. ISTo one was ever more passive in deduction, or described deductions with more candid sincerity. This is why supporters of different theses could use, and still can use, his writings, turn and turn about. When he expounds the cerebral determinism of intellectual activity, the materialists count him as their own; when he declares that thought and the brain are in the same relation as time and a clock, the spiritualists try to enlist him. In reality, he is just a physiologist handing over fresh facts to rejuvenate the speculator's endless wrangling.

In the narrower realm of physiology and medicine his admirable good faith explains the seeming contradiction between his scientific faith and his practical incredulity. He always had this double feeling in the highest degree, — that if medicine is to be sure of itself, it must have physiology as its necessary base, and that our presentday physiology is still far from supplying us with any practical certainty. He felt the full importance of his own discoveries as foundations for the medical edifice, but he did not share the illusions of those whose eagerness to transfer them to the realm of clinical or therapeutic applications often made him smile. The feeling for distances, which would have discouraged less valiant men, moved him not at all. For strength and perseverance, he did not need the intoxication of illusions. So he, who taught that medicine is or should be a science, showed himself thoroughly sceptical about physicians; and when he talked of them, the shade of Sganarelle ^ always seemed to pass before him.

The Introduction to the Study of Experimental Medicine marks a fresh phase in the life of Claude Bernard. From this period date the philosophic writings which opened the French Academy's doors to him. Of this period, too, are the books ^ in which grouping facts takes precedence over noting details, and in which he returns to his earlier discoveries and strives to bring his subsidiary work to the precision and perfection which present-day science permits.

This does not mean that he turned completely away from those regions of the unknown where he had formerly reaped such rich harvests. His latest work on the fundamental identity of the properties of tissues and of elementary functions in the animal and vegetable kingdoms, on anesthesia of the lower vegetables by chloroform or ether, and on the general action of toxic substances, shows that the creative spirit was still alive in him. Fresh discoveries were this year to have furnished another proof of his fertile activity. He confided this in part to his friends and pupils; and from the few words which escaped him, we may apparently conclude that the investigations which he carried out during his last vacation were to throw unexpected light on the theory of fermentation. This important work, of which he said, only four days ago, "What a pity ; it would have been good to finish it !" is lost to science.

* Recherches 8ur lea propriites des ti»8us viv<mt8. Lecon» de pathologie eaperimentale, etc. On December 31 he was stricken in the laboratory of the College de France ; shivering and fever soon came on, and special phenomena indicating inflammation of the kidneys. Nothing could stop the advance of a disease whose every progress he followed. Without any illusions about the fatal catastrophe, he observed with calm eyes, and with a smile denied his scientific family's pious lies. He was one of those whose gaze is undismayed by the unknown.

Personal feeling must be silent in this immense mourning of science, and yet, the loss of a great man is not all that moistens the eyes of those about his coffin: such kindliness, such simplicity of soul, such naive generosity were united in his genius. One's hand trembles in trying to sketch a few traits of this great and noble character. Nothing in his pure and harmonious life was turned aside from its chief aim. Enamored of literature, art and philosophy, Claude Bernard as a physiologist lost nothing by these noble passions; on the contrary, they all helped in developing the science with which he identified himself, and of which he is the highest and most complete embodiment. He was a physiologist such as no man had been before him. "Claude Bernard,'' said a foreign scientist, "is not merely a physiologist, he is physiology."

His very death seems to mark a new era in science. For the first time in our country, a man of science will receive those public honors hitherto reserved for political and military celebrities. The cabinet honored itself yesterday in asking parliament, which unanimously agreed to celebrate at state expense the solemn obsequies of the master who is no more. And one phrase of Gambetta, speaking in the name of the Budget Commission, sums up all that we have said : "The light, which has just been extinguished, cannot be replaced."

II. The a Priori Idea and Doubt in Experimental Reasoning 27 II. Experimental Considerations Peculiar to Living Beings 87 I. Examples of Experimental Physiological Investigation 151 To Conserve Health aj^d to Cube Disease : Medicine is still pursuing a scientific solution of this problem, which has confronted it from the first. ^ The present state of medical practice suggests that a solution is still far to seek. During its advance through the centuries, however, medicine has always been driven into action and from numberless ventures in the realm of empiricism has gained useful information. Though furrowed and overturned by all manner of systems so evanescent that, one by one, they have disappeared, it has none the less carried on research, acquired ideas and piled up precious materials which in due time will find their place and meaning in scientific medicine. To-day, thanks to the great development and powerful support of the physico-chemical sciences, study of the phenomena of life, both normal and pathological, has made progress which continues with surprising rapidity.

It is therefore clear to all unprejudiced minds that medicine is turning toward its permanent scientific path. By the very nature of its evolutionary advance, it is little by little abandoning the region of systems, to assume a more and more analytic form, and thus gradually to join in the method of investigation common to the experimental sciences. In order to embrace the medical problem as a whole, experimental medicine must include three basic parts : physiology, pathology and therapeutics. Knowledge of causes of the phenomena of life in the normal state, i.e., physiology, will teach us to maintain normal conditions of life and to conserve health. Knowledge of diseases and of their determining causes, i.e., pathology, will lead us, on the one hand, to prevent the development of morbid conditions,

*See Coura de pathologic expirimentale {Medical Times, 1859-1860). — Legon d'ouverture du cours de mSdecine du ColUge de France: Sur la midecine ex- p4rimentale (Gazette medicale. Paris, April 15, 1864; — Revue des cours scientifiques. Paris, Dec. 31, 1864.) and, on the other, to fight their results with medical agents, i.e., to cure the diseases. In the empirical period of medicine, which must doubtless still be greatly prolonged, physiology and therapeutics could advance separately; for as neither of them was well established, they were not called upon mutually to support each other in medical prac-, tice. But this cannot be so when medicine becomes scientific: it must then be founded on physiology. Since science can be established only by the comparative method, knowledge of pathological or abnormal conditions cannot be gained without previous knowledge of normal states, just as the therapeutic action of abnormal agents, or medicines, on the organism cannot be scientifically understood without first studying the physiological action of the normal agents which maintain the phenomena of life.

But scientific medicine, like the other sciences, can be established only by experimental means, i.e., by direct and rigorous application of reasoning to the facts furnished us by observation and experiment. Considered in itself, the experimental method is nothing but reasoning by whose help we methodically submit our ideas to experience, — the experience of facts. Reasoning is always the same, whether in the sciences that study living beings or in those concerned with inorganic bodies. But each kind of science presents different phenomena and complexities and difficulties of investigation peculiarly its own. As we shall later see, this makes the principles of experimentation incomparably harder to apply to medicine and the phenomena of living bodies than to physics and the phenomena of inorganic bodies.

Reasoning will always be correct when applied to accurate notions and precise facts; but it can lead only to error when the notions or facts on which it rests were originally tainted with error or inac^ curacy. That is why experimentation, or the art of securing rigorous and well-defined experiments, is the practical basis and, in a way, the executive branch of the experimental method as applied to medicine. If we mean to build up the biological sciences, and to study fruitfully the complex phenomena which occur in living beings, whether in the physiological or the pathological state, we must first of all lay down principles of experimentation, and then apply them to physiology, pathology and therapeutics. Experimentation is undeniably harder in medicine than in any other science ; but for that

very reason, it was never so necessary, and indeed so indispensable. The more complex the science, the more essential is it, in fact, to establish a good experimental standard, so as to secure comparable facts, free from sources of error. Nothing, I believe, is to-day so important to the progress of medicine. To be worthy of the name, an experimenter must be at once theorist and practitioner. While he must completely master the art of establishing experimental facts, which are the materials of science, he must also clearly understand the scientific principles which guide his reasoning through the varied experimental study of natural phenomena. We cannot separate these two things: head and hand. An able hand, without a head to direct it, is a blind tool ; the head is powerless without its executive hand.

The principles of experimental medicine will be explained in this work from the triple point of view of physiology, pathology and medicine. But before going into general considerations and special descriptions of the operative procedure proper to each of these divisions, I deem it useful to give a few explanations in this introduction in relation to the theoretic and philosophic side of the method which this book, after all, treats merely on its practical side.

The ideas which we shall here set forth are certainly by no means new ; the experimental method and experimentation were long ago introduced into the physico-chemical sciences, which owe them all their brilliancy. At different periods, eminent men have treated questions of method in the sciences; and in our own day Monsieur Chevreul, in all his works, is explaining very important ideas on the philosophy of experimental science. We shall therefore make no claim to philosophy. Our single aim is, and has always been, to help make the well-known principles of the experimental method pervade medical science. That is why we shall here recapitulate these principles, specially pointing out the precautions to be taken in their application, because of the very special complexity of the phenomena of life. We shall consider these difficulties, first in the use of experimental reasoning, and then in the practice of experimentation.

Only within very narrow boundaries can man observe the phenomena which surround him; most of them naturally escape his senses, and mere observation is not enough. To extend his knowledge, he has had to increase the power of his organs by means of special appliances; at the same time he has equipped himself with various instruments enabling him to penetrate inside of bodies, to dissociate them and to study their hidden parts. A necessary order may thus be established among the different processes of investigation or research, whether simple or complex : the first apply to those objects easiest to examine, for which our senses suffice; the second bring within our observation, by various means, objects and phenomena which would otherwise remain unknown to us forever, because in their natural state they are beyond our range. Investigation, now simple, again equipped and perfected, is therefore destined to make us discover and note the more or less hidden phenomena which surround us.

But man does not limit himself to seeing ; he thinks and insists on learning the meaning of the phenomena whose existence has been revealed to him by observation. So he reasons, compares facts, puts questions to them, and by the answers which he extracts, tests one by another. This sort of control, by means of reasoning and facts, is what constitutes experiment, properly speaking; and it is the only process that we have for teaching ourselves about the nature of things outside us.

In the philosophic sense, observation shows, and experiment teaches. This first distinction will serve as our starting point in examining the different definitions of observation and experiment devised by philosophers and physicians. Men sometimes seem to confuse experiment with observation. Bacon appears to combine them when be says: "Observation and experiment for gathering material, induction and deduction for elaborating it : tbese are our only good intellectual tools."

Physicians and physiologists, like most men of science, distinguish observation from experiment, but do not entirely agree in defining the two terms. Zimmermann ^ expresses himself as follows : "An experiment differs from an observation in this, that knowledge gained through observation seems to appear of itself, while that which an experiment brings us is the fruit of an effort that we make, with the object of knowing whether something exists or does not exist."

This definition embodies a rather generally accepted opinion. According to this definition, observation would be noting objects or phenomena, as nature usually presents them, while experiment would be noting phenomena created or defined by the experimenter. We should set up a sort of contrast, in this way, between observers and experimenters : the first being passive in the appearance of phenomena; the second, on the other hand, taking a direct and active part in producing them. Cuvier expressed the same thought in saying: "The observer listens to nature; the experimenter questions and forces her to unveil herself."