Popular Science Monthly/Volume 30/January 1887/The Experimental Study of Nature
By Dr. F. W. PAVY, F. R. S.
THE next part of my duty is to exhort the fellows and members of this college "to search and study out the secrets of Nature by way of experiment." These are the directions I am to follow, and they give me a wide field to select a course of procedure from. The kind of exhortation I shall employ will consist in placing before you a view of the method of work which Harvey himself adopted, and then, as an incentive to follow his example, I will display some of the fruit yielded by recent research conducted upon the lines of his procedure.
The object to be promoted is the acquirement of additional knowledge. It is an old but true saying that knowledge is power. We accept the doctrine, which comes to us in definite shape from no less ancient an authority than Aristotle, that there is no such thing as innate knowledge—that knowledge of every kind has to be acquired, and that it is based upon perceptions reaching the mind through the senses. Harvey thus epitomizes what was said by Aristotle respecting the manner in which the knowledge appertaining to science is acquired: "The thing perceived by sense remains; from the permanence of the thing perceived results memory; from multiplied memory, experience; and from experience, universal reason, definitions, and maxims or common axioms." In its elementary form, knowledge consists of simple inferences drawn in a direct manner from impressions. A child once burned afterward shuns the fire. From the impression received an inference is framed which forms the foundation for future action. The same kind of operation determines the conduct of the lower animals. By mental action these simple inferences may be raised into or give rise to knowledge of a higher kind. This is what for science is required to be done. The exercise of the intellectual faculties must be brought into operation, in order that what we acquire through perception may be shaped into the knowledge that it is desired to obtain. The object in science is to discover the facts and laws of Nature; and, to apply the intellect advantageously for the purpose, there must be some systematic course, some method or art of reasoning, adopted. The system employed up to Harvey's time was the Aristotelian, or syllogistic—a system which, while being well adapted for affording proof upon any particular point, is ill adapted for promoting the advance of knowledge. When through the major and minor premises of a syllogism I draw a conclusion, a point is proved, but no real addition is made to our stock of knowledge. For instance when in accordance with the rules of the syllogistic art I say—"All men are mortal: Thomas is a man, therefore Thomas is mortal"—I start with the general proposition in the major premise that "all men are mortal," and arrive at the conclusion, through the minor premise, that a particular individual is mortal. A certain attribute—mortality—is asserted to be possessed by a class. A member of the class must also possess the attribute, and this is all the information that my syllogistic conclusion has given me—that the individual named Thomas possesses the attribute of mortality, which belongs as a general character to the group of individuals of which he is a member. The two premises of the syllogism already consist of established truths, and for a syllogism to be valid there must be nothing contained in the conclusion beyond what is asserted in the premises. The train of reasoning, therefore, is not adapted to lead us to the acquirement of new knowledge. The essence, indeed, of the system consists in proceeding from generals to particulars. The major premise with which we start is, in reality, a general proposition, containing knowledge which has been acquired—not, it is true, by the methodical application of induction, but nevertheless after the manner of induction—by observation repeated and confirmed until the thing has come to be accepted as an established truth.
Harvey was shrewd enough to perceive that such a system of reasoning, which had continued in use up to the period in which he lived, did not assist in the disclosure of the secrets of Nature. He says: "The method of investigating truth commonly pursued at this time is to be held as erroneous and almost foolish, in which so many inquire what others have said, and omit to ask whether the things themselves be actually so or not; and single iiniversal conclusions being deduced from several premises, and analogies being thence shaped out, we have frequently mere verisimilitudes handed down to us instead of positive truths." Men's minds must have evidently now become occupied with the new system of philosophy set forth by Lord Bacon, in his "Novum Organum," or "True Directions Concerning the Interpretation of Nature." One of the aphorisms of this work clearly exhibits the difference between the new system and the old: "There are and can be only two ways of searching into and discovering truth. The one flies from the senses and particulars to the most general axioms, and from these principles, the truth of which it takes for settled and immovable, proceeds to judgment and to the discovery of middle axioms. The other derives axioms from the senses and particulars, rising by a gradual and unbroken ascent, so that it arrives at the most general axioms last of all." Upon system, or plan of procedure, a great deal depends: look at any undertaking carried out under a good system and a bad. The ancients were a long time in learning the right system to adopt, but it was indeed a great day for science when the method of reasoning by induction was introduced. Starting with particulars or facts which are collected from Nature by observation and experiment applied in every available way, it proceeds step by step in the process of generalizing until the largest and widest propositions are obtained. From the proposition which has been formulated out of, it may be, only a few facts, advance is made with the aid of other facts to propositions of a more and more general character. The unknown is brought into the domain of the known, and as this domain increases, not only is the position acquired strengthened, but at the same time rendered more advantageous for the attainment of further extension. Thus the march onward proceeds, and when some general law of Nature—like, for instance, gravitation, the correlation of the physical forces, or, even, with a more limited bearing, reflex spinal action—is discovered, a gain is made which, through reflected influence, has the effect of at once immensely enlarging and perfecting the understanding. Truly, it may be said, the explorer by the inductive method does not know whither he may be led. He dedicates himself
"To unpathed waters—undreamed shores,"
and follows simply the direction indicated to be taken by what happens to be revealed. Guided entirely by the facts disclosed by observation and experiment, he brings the instrumental agency of the mind as a reasoning power to bear upon them, and draws from them that which adds to the store of knowledge already possessed. He seeks for facts and interprets their meaning as they come before him. This was the course pursued by Harvey. Instead of giving himself up, as others had done before him, to arguing out conclusions from accepted axioms, he struck out into the hitherto untrodden path of inquiry—that of induction—and sought knowledge by a direct appeal to Nature through the medium of observation and experiment. "It were disgraceful," he says, "with this most spacious and admirable realm of Nature before us, did we take the reports of others upon trust, and go on coining crude problems out of these, and on them hanging knotty and captious and petty disputations. Nature is herself to be addressed; the paths she shows us are to be boldly trodden."
In the discovery of the circulation, Harvey applied the principles of induction, and argued upon them in a strictly logical way. He showed himself to be a good and careful observer, judged even by the standard set forth in the following words of John Stuart Mill, on the process of observing. "The observer," says Mill, "is not he who merely sees the thing which is before his eyes, but he who sees what parts that thing is composed of. To do this well is a rare talent. One person, from inattention, or attending only in the wrong place, overlooks half of what he sees. Another sets down much more than he sees, confounding it with what he imagines or with what he infers. Another takes note of the kind of all the circumstances, but, being inexpert in estimating their degree, leaves the quantity of each vague and uncertain. Another sees, indeed, the whole, but makes such an awkward division of it into parts, throwing things into one mass which require to be separated, and separating others which might more conveniently be considered as one, that the result is much the same, sometimes even worse, than if no analysis had been attempted at all, It would be possible to point out what qualities of mind and modes of mental culture fit a person for being a good observer; that, however, is a question not of logic, but of the theory of education, in the most enlarged sense of the term."
The experiments which Harvey conducted on the arteries and veins to assist him in his inquiry were founded upon a well-devised plan. It may be said of experiment, that it affords the means of varying the circumstances, and thus aids immensely the acquirement of knowledge by induction. In the application of the faculties to discovery, the mind asks itself what facts are needed to assist in the establishment of a correct conclusion. The fact may be looked for among the varied instances presented by Nature; or, by an artificial arrangement of circumstances, the required instance may be made—in other words, experiment may be had recourse to for supplying what is wanted. In the one case, we get our fact by observation from the variations in the circumstances spontaneously furnished by Nature; in the other, we obtain it from experiment, which possesses the great advantage over observation not only of furnishing us with a much greater number of variations than is to be found naturally presented, but also of enabling us to produce the precise form of combination or variation which is needed for our purpose.
Harvey, in a true sense, adopted the Baconian system of interrogating Nature by appeal to observation and experiment, and drawing conclusions out of the facts presented, and yet it is evident that the Novum Organum" was not published till after the discovery of the circulation was made. Bacon's new method of conducting research and discovering the truths of Nature was placed before the public in 1620. Harvey's work on the circulation, "Exercitatio Anatomica de Motu Cordis et Sanguinis Animalibus," was not "published till 1628, but it has been generally allowed that his discovery was made known in his first course of Lumleian lectures, delivered at the college in 1616; and, thanks to the meritorious labors of a committee of the college, this has now been rendered open to verification by the very interesting volume just prepared, and on the point of being issued, containing a reproduction in autotype form of his original lecture-notes in his own handwriting. Harvey, then, must have been thoroughly in the van of progress taking place in his day; and, further, the contemporaries of Bacon must have been acquainted with the new system of philosophy before the "Novum Organum" was published.
Harvey's discovery established a new departure in physiology. Without a knowledge of the circulation, nothing really could be known about the various operations taking place within us. It is hard, with the knowledge now possessed, to realize the state existing at the time the circulation was discovered. The passage of blood from the right to the left side of the heart had, it is true, already been recognized, but it was taught that the blood went to the lungs for their nutrition, and "to be elaborated and subtilized by the reception of a spirit from the air in inspiration, and the exhalation of a fuliginous matter in expiration." The heart and arteries were supposed to be the seat of the vital spirit, and the liver to be the fountain whence the body was supplied with blood through the veins, in which there was believed to be a to-and-fro current, a flux and reflux, that was compared to the ebb and flow of the tide in the classic straits of Euripus. Truly, indeed, may it be asserted, that our ancestors stand in the twofold position of our parents with respect to age, our children with respect to knowledge.
It was not without opposition that Harvey's views were received; and the high position in his profession he had attained did not suffice to prevent his escape from the effect of the prejudice against innovation entertained by the multitude. Aubrey tells us he had "heard him say that after his book on the circulation of the blood came out, he fell mightily in his practice; 'twas believed by the vulgar that he was crack-brained, and all the physicians were against him." Harvey lived, however, to see his doctrine generally accepted. But such are the vicissitudes of time, that in our day an attempt has been made to deprive him of the title of discoverer of the circulation, and give it to an Italian physician, Cesalpino, because it has been found that a few words of what he wrote can be construed into suggesting that a conception of the circulation existed in his mind. Most ably and successfully have my predecessors in the delivery of this oration. Sir Edward Sieveking and Dr.George Johnson, combated the claim that has been put forward on behalf of Cesalpino, and maintained the position of Harvey.
Science prepares the ground for the exercise of art. The one—science—is concerned with knowledge as knowledge; the other, with the application of it to a practical end. Our art—our raison d'être as members of the medical profession—is to apply the knowledge of medical science to the prevention of, cure or mitigation of, and alleviation of the sufferings from disease—to secure, in fact, for man as natural a passage through life as happens to be attainable. We can not prevent death. Lord Bacon, in his essay "De Morte," said:
"Æque enim est naturale hominibus mori, ac nasci."
True, it is as natural to die as to be born; and Nature's laws must be complied with. Our aim is to avert premature death. A certain power, given to us at starting upon our existence, carries us on, under exposure to the proper conditions or influences for keeping this power going. But, in the exercise of its action, although for a while it shows no signs of a failing tendency, yet assuredly it progresses toward exhaustion and ultimate extinction. Accompanying, and doubtless dependent on, the declining power, and assisting in leading to its becoming extinguished, there is an advancing deterioration of the material organism in which the power is manifested. Such is what is natural; but many circumstances contribute to avert the natural, the ordinary course being run. The power given to start with may not be equal to the standard, and the issue of generation may, in consequence, present itself under a weak and ill-developed form, easily falling a victim to influences that there ought to be strength enough to resist. There may be a taint in the power derived by generation from the parents—something transmitted by inheritance, which may give rise to a tendency to the development of some structural deviation from the natural state, or to the performance of one or other functional operation of life, in a manner that does not conform with what may be said to be strictly natural. It is a law of Nature for the offspring, more or less closely, to assume the likeness of the parent, and likeness in the shape of what is wrong may be assumed as well as in the shape of what is right.
Quitting the quality of the power given to us to start with, we are next dependent upon the influences derived from the external or surrounding conditions to which we become exposed. Light, air, what we eat and drink, or what in any way gets into the system, temperature, exercise of mind and body—in short, the conditions under which we live—all exert their influence in favoring or otherwise a natural passage through life. Within us, operations forming a part of the operations of Nature proceed, but these operations are influenced by—owe their activity, indeed, to—the surrounding conditions, and thus it is that upon these surrounding conditions depends whether a natural course is run or not. Under the same law, these surrounding conditions may exert a modifying influence in this or that particular direction upon the operations that are proceeding, and by long continuance in force may lead to the establishment of a more or less modified state as a part of our nature, in accordance with the Darwinian principle of natural selection. This matter—the modifications for good or bad, wrought in our nature by the influence of external conditions—embraces a wide field of study, and comprehends nothing less than the possession of a knowledge of the varied operations, with the laws determining them, going on around us, in order that we may understand the manner in which they are brought about. It is a vast subject, but the mind of man has already done much, and there is reason to think will do much more, toward penetrating it; and, as with the amount of knowledge acquired, power is possessed—that is, the power of arranging conditions or operations so as to render them subservient to the production of a desired effect—man stands in the position of an increasingly powerful agent in the realm of Nature. Must not the mind itself, then, through which this is accomplished, be reckoned as a power—a great power among the powers of the universe? In our special department as medical practitioners, it falls to us to apply the power which knowledge gives us toward preventing unnatural conditions of the body from being allowed to become developed, and toward bringing the unnatural back into the natural state—in fact, toward aiding in carrying life on in a natural manner through its ordinary term of existence.—Lancet.