The standing of this pioneer endeavor as a pedagogic proposition, as a scientific method, we may attempt to justify at the present writ ing under six heads. The first of these heads we may suggest as the substantiality and the variety of the physiologic principles that can thus be studied.
A second possible feature of this manner of teaching elementary physiology has been alluded to by implication already: the transparency and the smallness of the animals used make more striking and easy of acceptance the essential unification of parts into the animal whole. In Daphnia this is notable in the interest a first viewing of the animalcule invariably excites whether in man or child. One actually sees, for example, the blood corpuscles that are kept in circulation by the heart pulsating under the ob server's eye; and the intestinal peristalsis can be actually seen to advance up the gut in relation with the pulsations of the digestive gland. Here is unification too obvious to be missed even by the careless child. Without a comprehension of the interdependence of his bodily parts he can learn neither to understand himself nor how to keep well! A third advantage of such a course lies in the simplicity and the inexpensiveness of the apparatus required. Many elementary schools have compound microscopes, and every school or even every student could provide at least a strong pocket-lens, which might be made to suffice. Beyond the microscope the apparatus required is almost nothing not afforded by every laboratory of chemistry, if we except a few always-present implements such as a watch, a millimeter rule and small and simple glassware. To those of us who know the considerable ex pense of most of the apparatus that we use this factor will appeal. At any rate, it puts this course within range of any school, no mat ter how simple or indigent or isolated, and makes more affluent schools more independent than heretofore of the avaricious apparatus dealer.
In similar manner, the life-material required is always obtainable with great ease and with little or no expense, summer or winter, and throughout the world. As is well known, these animals have an almost earth-wide distribution and are easily gathered from pools and streams. If this be not convenient, a few cents for postage brings most of these animalcules within easy reach of such few schools as for special reasons might not care to maintain the simple jar-aquaria for breeding them. They come in such countless numbers so readily that whoever made a business of supplying them could not conscientiously, one would hope, charge for them more than the smallest public class could easily pay.
Ease of maintenance of the animalcules is an advantage close to that just mentioned. In stead of ill-smelling animal-rooms expensive to maintain, containing unhappy large animals often both hard and expensive to properly feed, the animalcules are kept in more or less at tractive glass aquaria that need contain no more than a few litres of water each for use of large classes. Many of these little animals maintain themselves year after year. Daphnia, for example, not ((running out') as long as one uses just ordinary intelligence in imitating a simple environment somewhere near that which is natural to it. The infusoria. of course, Stentor, Paramecium, etc., can be readily de veloped at any time in two weeks from old leaves and hay and similar commonplace ma terial, everywhere and always at hand.
No one with a guirkless brain can nowadays fail to justify vivisection by competent scien tists, but many, nonetheless, men as well as women and children, savants as well as fools, dislike to do this work, especially for purposes of routine class-instruction. This repugnance to blood-shedding and mutilation is obviously a necessary human feeling worthy to be culti vated rather than blunted. (In the vivisection polemics one sees too seldom perhaps due credit given us animal-experimentalists for the per formance of disagreeable death and mutilation on animals whom we of all men best appreciate at their marvelous value and perfection). Strangely enough, the size of the animal is a factor in the determination of the strength of this feeling of repugnance to mutilation found in all normal human beings, while another of its tleterminants is complexity. Men of culture who would hesitate to kill a mouse or to drown a puppy have no such feelings ordinarily in re gard to ants, however wonderfully efficient in their complex living, or in regard to the medusoids, however large and conspicuous. Thus the animalcules may be adequately studied by young or old, by boys and girls, without a prohibitive feeling of repugnance to the destruc tion of life. This circumstance is both justifi able biologically and ethically and practically convenient for teaching purposes, and gives the animalcules an advantage for scientific purposes not easy to exaggerate.