The relations of physiology need not detain us long. Those most obvious and close are with biology as the general science of life; to anat omy as a comparatively narrow phase of mor phology; to chemistry; to hygiene, part of which of course is physiology applied to the maintenance of health as long as possible; to therapeutics; to neurology; to psychology in all its protean forms; to philosophy, and even at times and in certain minds to metaphysics. The self-respecting physiologist is invariably a fairly good student of biology, and if he knows nothing and cares less about metaphysics, at least it is undeniably true that the metaphysi cian no longer snorts at the suggestion that a little physiology would not hurt his wisdom,— although he seldom or never acts on the notion.
Applications of physiology. Without talk ing much about it or making it very explicit in the public mind, physiology has far outdis tanced psychology in applying itself usefully to life, and yet scarcely a beginning has been made, especially since the applications of physi ology scarcely realize that they are applications. In one sense, and to a degree, the applications of physiology were made before the physiology itself.
In the days of Oliver Wendell Holmes, for example, one man, with some assistants prob ably, taught all the anatomy and physiology that was given in the Harvard Medical School. As things were just before the great World War began, at least 20 men, each of whom probably knows more of medicine than Oliver Wendell Holmes (great as are his contributions to med ical science and to literature), instructed in anatomy and physiology in the same school, and the annual budget of these two departments was certainly several times the entire income for the sale of course-tickets in Dr. Holmes' day. Much of this money to be sure is expended in expensive practical work rather than in salaries for mere lectures.
Among the most obvious applications of physiology are those seen in physical education, especially in the physiology of exercise; in med icine; in general education; and the most re cent of them is to the orthopedic re-education of the maimed and crippled, and those suffer ing from war neuroses sometimes still called ((shell-shock.'' Methods.— Physiology is slightly deductive from the principles of biology and from struc ture. Although it is certain that no one could discover the action of some machines from the unmoving machine itself, it is equally true that other mechanisms bear in their very structure, so to say, a moving picture of their action. In
no mechanism or near-mechanism perhaps is this less true than it is of organisms, the reason for this being apparently the minute complexity of many of its mechanisms. The heart, for ex ample, certainly bears in its anatomy its mode of action, for it is in part a matter of direction of blood-stream through unalterable valves workable only in one direction; on the other hand, decades of study were required to ex plain under what precise conditions the heart contracted, in relation to the nervous-system.
The failure of deduction as a physiological method has its most striking example in the brain, and it is in a degree literally true that the men who really knew most about the human brain are those least certain of its processes a statement of which elementary students of physiology delight to remind their instructor just before examination! Physiology is largely inductive from experi mentation. For one good guess made by the physiologist with imagination, at least a hun dred more or less important facts have been discovered by experiment, often elaborate be yond the comprehension of the untechnical. No science is more inductive than physiology. Laboratory-physiology is a highly complex art in itself, an art continually changing, and we may say, simplifying, reducing itself to its low est terms. Many of the greatest discoveries of modern times have been made by mechanisms of the simplest type, which differ from those employed in previous researches by being underlaid by an ingenious new idea.
A glance at any of the laboratory-manuals of physiology, such as that for example of Cannon, published by the Harvard University Press, shows how instructive and at the same time how elaborate and expensive of time and money such a course to-day must be The present writer, if he may be allowed to intrude a bit of his work, has already developed a laboratory course in physiology, suitable for elementary and secondary girls' schools of all grades, and dealing wholly with animalculm. This article summarizes itself as follows: One finds here basal and important princi ples of universal physiology, and the ingenuity of other experienced physiologists would surely indicate and define many principles more. The essentials of much physiology certainly are present in experimentation of this relatively simple kind.