An Introduction to the Study of Experimental Medicine

Laplace considers astronomy a science of observation, because we can only observe the movements of the planets ; we cannot reach them, indeed, to alter their course and to experiment v^^ith them. ^^On earth," said Laplace, "we make phenomena vary by experiments ; in the sky, we carefully define all the phenomena presented to us by celestial motion." ^ Certain physicians call medicine a science of observations, because they wrongly think that experimentation is inapplicable to it.

Fundamentally, all sciences reason in the same way and aim at the same object. They all try to reach knowledge of the law of phenomena, so as to foresee, vary or master phenomena. Astronomers foretell the movements of the stars; they deduce from them a quantity of practical ideas; but they cannot alter celestial phenomena by experimentation as do chemists and physicists the phenomena of their sciences. If then, from the point of view of philosophic method, there is no essential difference between sciences of observation and sciences of experimentation, still there is a real one from the point of view of the practical consequences, which man deduces from them, and the power which he gains by their means. In sciences of observation, man observes and reasons expeiimentally, but he does not experiment; and in this sense we might say that a science of observation is a passive science. In sciences of experimentation, man observes, but in addition he acts on matter, analyzes its properties and to his own advantage brings about the appearance of phenomena which doubtless always occur according to natural laws, but in conditions which nature often has not yet achieved. With the help of these active experimental sciences, man becomes an inventor of phenomena, a real foreman of creation; and under this head we cannot set limits to the power that he may gain over nature through future progress in the experimental sciences.

The question remains whether medicine should continue a science of observation or become an experimental science. Medicine must doubtless begin as simple clinical observation. Then, since the human organism is in itself a harmonious unit, a little world (microcosm) contained in the great world (macrocosm), men have actually maintained that life is indivisible and that we should limit ourselves to observing the phenomena presented to us as a whole by living organisms, whether well or sick, and should content ourselves with reasoning on the facts observed. But if we admit that we must so limit ourselves, and if we posit as a principle that medicine is only a passive science of observation, then physicians should no more touch the human body than astronomers touch the planets. Hence, normal and pathological anatomy, vivisection applied to physiology, pathology and therapeutics, — all would become completely useless. Medicine so conceived can lead only to prognosis and to hygienic prescriptions of doubtful utility; it is the negation of active medicine, i.e., of real and scientific therapeutics.

This is by no means the place to begin examining so important a definition as that of experimental medicine. I propose to treat this question later with all necessary amplification. I shall limit myself here to saying that I think that medicine is destined to be an experimental and progressive science; and precisely because of my conviction in this respect, I am putting together this work with the object of contributing my share toward encouraging the development of scientific and experimental medicine.

Despite the important difference, which we have just pointed out, between the so-called sciences of observation and of experimentation, observers and experimenters still have the common and immediate object, in their investigations, of establishing and noting facts and phenomena as rigorously as possible, and with the help of the most appropriate means ; they behave exactly as if they were dealing with two ordinary observations. In both cases, indeed, a fact is simply noted ; the only difference is this, — as the fact which an experimenter must verify does not present itself to him naturally, he must make it appear, i.e., induce it, for a special reason and with a definite object. Hence we may say that an experiment is fundamentally just an observation induced with some object or other. In the experimental method, search for facts, i.e., investigation, is always accompanied by reasoning, so that experimenters usually make an experiment to control or verify the value of an experimental idea. Hence, in this

case, the experiment is an observation induced with the object of control. Still, to complete our definition and to extend it to the sciences of observation, it is worth recalling here that, to verify an idea, it is not always absolutely necessary to make an experiment or an observation ourselves. We shall have recourse to experimentation perforce only when the observation to be induced is not already prepared in nature. But if an observation has already been made, either naturally or accidentally, or even by another investigator, then we may take it ready made, and produce it simply to serve as verification of the experimental idea. And this may be summed up again by saying that, in this case, the experiment is just an observation produced for the purpose of control. It follows that, to reason experimentally,, we must usually have an idea and afterwards induce or produce facts, i.e., observations, to control our preconceived idea.

We shall examine later the importance of preconceived experimental ideas; let it suffice us now to say that the idea, by virtue of which we undertake an experiment, may be more or less clearly defined, according to the nature of the subject and according to the state of perfection of the science in which we are experimenting. Indeed the guiding idea of an experiment should include everything already known about the subject, so as to direct our search more surely toward problems whose solution may be fruitful in the advancement of science. In established sciences, like physics and chemistry, experimental ideas are deduced in logical sequence from ruling theories, and are submitted with a clearly defined meaning to the control of experiment ; but in the case of a. science in its infancy, like medicine, where complex and obscure questions are still to be studied, experimental ideas do not always emerge from rather vague conceptions. What then must be done? Must we abstain and wait for observations to present themselves spontaneously and so bring us clearer ideas? We might often wait long and even in vain; in any case we gain by experimenting. But in this instance we can guide ourselves only by a kind of intuition, as we catch sight of probabilities; and if the subject is entirely dark and unexplored, physiologists should not be afraid even to act somewhat at random, so as to try, — permit me the common expression, — fishing in troubled waters. This amounts to saying that, in the midst of the functional disturbances which they produce, they may hope to see some unex-

pected phenomena emerge which may give direction to their research. Such groping experiments, which are very common in physiology and therapeutics because of the complex and backward state of these sciences, may be called experiments to see, because they are intended to make a first observation emerge, unforeseen and undetermined in advance, but whose appearance may suggest an experimental idea and open a path for research. There are instances, then, in which we experiment without having a probable idea to verify. However, experimentation in this instance is none the less intended to induce an observation, only it induces it with a view to finding an idea which shall point out a later path to follow in investigation. We may therefore say that the experiment is then an observation induced with the object of bringing to birth an idea.

To sum up, the investigator seeks and concludes ; he includes both observations and experiments, he pursues the discovery of new ideas, even while seeking facts from which to draw a conclusion, or an experiment calculated to control other ideas. In a general and abstract sense, an experimenter, then, is a man who produces or induces, in definite conditions, observed facts, to derive from them the instruction which he wishes, — that is, experience. An observer is a man who gathers observed facts and who decides whether they have been ascertained by the help of appropriate means. Thus it is that experimenters must at the same time be good observers, and that in the experimental method, experiment and observation always advance side by side.

Men of science who mean to embrace the principles of the experimental method as a whole, must fulfill two classes of conditions and must possess two qualities of mind which are indispensable if they are to reach their goal and succeed in the discovery of truth. First, they must have ideas which they submit to the control of facts ; but at the same time they must make sure that the facts which serve as starting point or as control for the idea are correct and well established ; they must be at once observers and experimenters.

Observers, we said, purely and simply not© the phenomena before their eyes. They must be anxious only to forearm themselves against errors of observation which might make them incompletely see or poorly define a phenomenon. To this end they use every instrument which may help make their observations more complete. Observers, then, must be photographers of phenomena ; their observations must accurately represent nature. We must observe without any preconceived idea; the observer's mind must be passive, that is, must hold its peace; it listens to nature and writes at nature's dictation.

But when a fact is once noted and a phenomenon well observed, reasoning intervenes, and the experimenter steps forward to interpret the phenomenon. An experimenter, as we have already said, is a man inspired by a more or less probable but anticipated interpretation of observed phenomena, to devise experiments which, in the logical order of his anticipations, shall bring results serving as controls for his hypothesis or preconceived idea. To do this, an exp>erimenter reflects, tries out, gropes, compares, contrives, so as to find the experimental conditions best suited to gain the end which he sets before him. Of necessity we experiment with a preconceived idea. An experimenter's mind must be active, i.e., must question nature, and put all manner of queries to it according to the various hypotheses which suggest themselves.

But when the conditions of an experiment are once established and worked up according to the mind's preconceived idea, an induced or premeditated observation will, as we said, result. Phenomena then appear which the experimenter has caused, but which must now be noted, so as to learn next how to use them to control the experimental idea which brought them to birth. !Now, from the moment when the result of an experiment appears, the experimenter is confronted with a real observation which he has induced and must note, like any other observation, without any preconceived idea. The experimenter must now disappear or rather change himself instantly into an observer; and it is only after he has noted the results of the experiment exactly, like those of an ordinary observation, that his mind will come back, to reason, compare and decide whether his experimental hypothesis is verified or disproved by these very results. To maintain the comparison suggested above, I may say that our experimenter puts questions to nature ; but that, as soon as she speaks, he must hold his peace ; he must note her answer, hear

her out and in every case accept her decision. It has been said that the experimenter must force nature to unveil herself. Yes, the experimenter doubtless forces nature to unveil herself by attacking her with all manner of questions; he must never ansv^er for her nor listen partially to her answers by taking, from the results of an experiment, only those which support or confirm his hypothesis. We shall see later that this is one of the great stumbling blocks of the experimental method. An experimenter, who clings to his preconceived idea and notes the results of his experiment only from this point of view, falls inevitably into error, because he fails to note what he has not foreseen and so makes a partial observation. An experimenter must not hold to his idea, except as a means of inviting an answer from nature. But he must submit his idea to nature and be ready to abandon, to alter or to supplant it, in accordance with what he learns from observing the phenomena which, he has induced.

Two operations must therefore be considered in any experiment. The first consists in premeditating and bringing to pass the conditions of the experiment; the second consists in noting the results of the experiment. It is impossible to devise an experiment without a preconceived idea ; devising an experiment, we said, is putting a question ; we never conceive a question without an idea which invites an answer. I consider it, therefore, an absolute principle that experiments must always be devised in view of a preconceived idea, no matter if the idea be not very clear nor very well defined. As for noting the results of the experiment, which is itself only an induced observation, I posit it similarly as a principle that we must here, aB always, observe without a preconceived idea.

In the experimenter, we might also differentiate and separate the man who preconceives and devises an experiment from the man who carries it out or notes its results. In the former, it is the scientific investigator's mind that acts; in the latter, it is the senses that observe and note. What I am setting forth is most strikingly proved in the case of Francois Huber.^ Though blind, this great naturalist left us admirable experiments which he conceived and afterward had carried out by his serving man, who, for his part, had not a single scientific idea. So Huber was the directing mind that

' Francois Huber, 'Nouvelles Observations sur les Aheilles, 2nd edition, expanded by hi^ son, Pierre Huber, Geneva, 1814. devised the experiment ; but he was forced to borrow anotber's senses. The serving man stood for tbe passive senses, obedient to tbe mind in carrying out an experiment devised in tbe ligbt of a preconceived idea. People wbo condemn tbe use of bypotbeses and of preconceived ideas in tbe experimental method make tbe mistake of confusing invention of an experiment with noting its results. We may truly say that tbe results of an experiment must be noted by a mind stripped of bypotbeses and preconceived ideas. But we must beware of proscribing the use of bypotbeses and of ideas wben devising experiments or imagining means of observation. On tbe contrary, as we shall soon see, we must give free rein to our imagination; tbe idea is tbe essence of all reasoning and all invention. All progress depends on tbat. It cannot be smothered or driven away on tbe pretence tbat it may do barm ; it must only be regulated and given a criterion, wbich is quite anotber matter.

Tbe true scientist is one wbose work includes both experimental tbeory and experimental practice. (1) He notes a fact; (2) a propos of tbis fact, an idea is bom in bis mind; (3) in tbe ligbt of tbis idea, be reasons, devises an experiment, imagines and brings to pass its material conditions ; (4) from tbis experiment, new phenomena result wbicb must be observed, and so on and so forth. Tbe mind of a scientist is always placed, as it were, between two observations: one wbicb serves as starting point for reasoning, and tbe other wbicb serves as conclusion.

To make myself clearer, I bave endeavored to separate tbe different operations of experimental reasoning. But wben it all takes place at tbe same time in tbe bead of a scientist, abandoning bimself to investigation in a science as vague as medicine still is, tben tbe results of observation are so entangled witb tbe bases of experiment tbat it would be alike impossible and useless to try to dissociate, from their inextricable mingling, eacb one of these terms. It is enougb to remember tbe principle that an a priori idea, or better, an bypotbesis, is a stimulus to experiment, and tbat we must let ourselves go witb it freely, provided tbat we observe tbe results of our experiment rigorously and fully. If an bypotbesis is not verified and disappears, tbe facts wbicb it bas enabled us to find are none tbe less acquired as indestructible materials for science.

Observers and experimenters, tben, correspond to different phases of experimental research. The observer does not reason, he notes; the experimenter, on the other hand, reasons and grounds himself on acquired facts, to imagine and induce rationally other facts. But though in theory and abstractly we may differentiate observers from experimenters, it seems impossible to separate them in practice, since we see that one and the same investigator, perforce, is alternately observer and experimenter.

Things happen constantly, indeed, in this way when a single man of science discovers and explains a whole scientific question unaided. But it more often happens in the evolution of science, that different parts of experimental reasoning are shared by several men. Some of these, both in medicine and in natural history, merely gather and assemble observations; others manage to formulate more or less ingenious and more or less probable hypotheses based on these observations; then others come in to create conditions favoring the birth of an experiment to control these hypotheses; finally others apply themselves more especially to generalizing and systematizing the results obtained by the different observers and experimenters. This parceling out of the experimental domain is useful, because each one of its various parts is all the better cultivated. In fact we can easily conceive that, in certain sciences, the means of observation and experimentation are such specialized instruments that their management and use require a certain manual dexterity or the sharpening of certain senses. But while I accept specialization in the practice, I reject it utterly in the theory of science. I believe, indeed, that making generalization one's specialty is anti-philosophic and antiscientific, in spite of what has been proclaimed by a modern philosophic school which piques itself on its scientific basis.

Experimental science, however, cannot advance on a single side of the method taken separately; it goes ahead only by the union of all parts of the method converging toward a common goal. Men who gather observations are useful only because their observations are afterward introduced into experimental reasoning; in other words, endless accumulation of observations leads nowhere. Men, who formulate hypotheses a propos of observations gathered by others, are useful only in so far as men seek to verify these hypotheses by experimenting; else these hypotheses, unverified or unverifiable by experiment, would engender nothing but systems and would bring us back to scholasticism. Men who experiment, despite all their dex-

terity, cannot solve problems unless they are inspired by a fortunate hypothesis based on accurate and well-made observations. Finally men who generalize can make lasting theories only in so far as they themselves learn all the scientific details that these theories are intended to represent. Scientific generalization must proceed from particular facts to principles ; and principles are the more stable as they rest on deeper details, just as a stake is the firmer, the farther it is driven into the ground.

We see, then, that the elements of the scientific method are interrelated. Facts are necessary materials; but their working up by experimental reasoning, i.e., by theory, is what establishes and really builds up science. Ideas, given form by facts, embody science. A scientific hypothesis is merely a scientific idea, preconceived or previsioned. A theory is merely a scientific idea controlled by experiment. Reasoning merely gives a form to our ideas, so that everything, first and last, leads back to an idea. The idea is what establishes, as we shall see, the starting point or the primum movens of all scientific reasoning, and it is also the goal in the mind's aspiration toward the unknown.

Everyone first works out his own ideas about what he sees and is inclined to interpret natural phenomena by anticipation before knowing them through experience. This tendency is spontaneous; a preconceived idea always has been and always will be the first flight of an investigating mind. But the object of the experimental method is to transform this a priori conception, based on an intuition or a vague feeling about the nature of things, into an a posteriori interpretation founded on the experimental study of phenomena. This is why the experimental method is also called the a posteriori method.

Man is by nature metaphysical and proud. He has gone so far as to think that the idealistic creations of his mind, which correspond to his feelings, also represent reality. Hence it follows that the experimental method is by no means primitive or natural to man, and that only after lengthy wanderings in theological and scholastic discussion has he recognized at last the sterility of his efforts in this direction. At this point man becomes aware that he cannot dictate laws to nature, because he does not contain within himself the knowledge and criterion of external things, and he understands that to find truth he must, on the contrary, study natural laws and submit his ideas, if not his reason, to experience, that is, to the criterion of facts. Yet for all that, the method of work of the human mind is not changed at bottoni. The metaphysician, the scholastic, and the experimenter all work with an a priori idea. The difference is that the scholastic imposes his idea as an absolute truth which he has found, and from which he then deduces consequences by logic alone. The more modest experimenter, on the other hand, states an idea as a question, as an interpretative, more or less probable anticipation of nature, from which he logically deduces consequences which, moment by moment, he confronts with reality by means of experiment. He advances, thus, from partial to more general truths, but without ever daring to assert that he has grasped the absolute truth.

Indeed if we held it at any point whatever, we should have it everywhere ; for the absolute leaves nothing outside itself. An experimental idea, then, is also an a priori idea, but it is an idea that presents itself in the form of an hypothesis the consequences of which must be submitted to the criterion of experiment, so that its value may be tested. The experimenter's mind differs from the metaphysician's or the scholastic's in its modesty, because experiment makes him, moment by moment, conscious of both his relative and his absolute ignorance. In teaching man, experimental science results in lessening his pride more and more by proving to him everyday that primary causes, like the objective reality of things, will be hidden from him forever and that he can know onlv relations. Here is, indeed, the one goal of all the sciences, as we shall see further on.

The human mind has at different periods of its evolution passed successively through feeling, reason and experiment. First, feeling alone, imposing itself on reason, created the truths of faith or theology. Reason or philosophy, the mind's next mistress, brought to birth scholasticism. At last, experiment, or the study of natural phenomena, taught man that the truths of the outer world are to be found ready formulated neither in feeling nor in reason. These are indispensable merely as guides; but to attain external truths we must of necessity go down into the objective reality of things where they lie hidden in their phenomenal form.

Thus, in the natural progress of things, appeared the experimental method which includes everything and which, as we shall soon see, leans successively on the three divisions of that unchangeable tripod ; sentiment, reason and experiment. In the search for truth by means of this method, feeling always takes the lead, it begets the a priori idea or intuition ; reason or reasoning develops the idea and deduces its logical consequences. But if feeling must be clarified by the light of reason, reason in turn must be guided by experiment.

The experimental method is concerned only with the search for objective truths, not with any search for subjective truths. As there are two kinds of functions in man's body, the first, conscious functions, the rest not, so in his mind there are two kinds of truths or notions, some conscious, inner or subjective, the others unconscious, outer or objective. Subjective truths are those flowing from principles of which the mind is conscious, and which bring it the sensation of absolute and necessary evidence. The greatest truths, indeed, are at bottom simply a feeling in our mind; that is what Descartes meant by his famous aphorism.