Page:Popular Science Monthly Volume 30.djvu/654

632 training after that period is one adapted, if not intended to repress the forms of observation, and hence the first thing to be taught a student on entering the biological laboratory in one of the institutions of the better class is how to observe. This, though it appears an easy task, is really one of considerable difficulty. First, there is a tendency to consult books so as to learn what is or should be seen; and, secondly, there is a sudden jumping at conclusions from the most superficial examination of the specimen, and these conclusions are adhered to most tenaciously, utterly preventing the formation of any different view.

Together with the formation of habits of observation, it is desirable that a certain amount of facts be obtained, and so the student is set at the dissection of a selected series of animal types; for instance, the sea-anemone, sea-urchin, earth-worm, lobster, clam, and frog. Economy of material is insisted upon, and the admonition is frequently given that each stroke of the scalpel should mean something. Drawing is extremely essential, for, if the student be made to draw exactly what he sees, he will have to look more closely, and, at the same time, the instructor can readily see exactly how well his pupil works, and exactly where his difficulties lie. At first the student declares he can not draw, that he has not the slightest taste for art, and yet, after a very little experience, he makes thoroughly intelligible, if not artistic, representations of what he sees.

A very important point in making these small dissections is making them under water. If one attempt to dissect a clam in the open air, the various parts will settle down and adhere to each other; while, if the operation be performed under water, this difficulty will be avoided, the parts being buoyed up by the surrounding medium. To trace the course of the blood-vessels, injections are resorted to. Some quickly hardening mass, like plaster-of-Paris or melted wax, or gelatine colored by carmine, vermilion, or Prussian blue, is forced into the arteries or veins, and then the student, by following the streaks of color, can readily follow the course of the circulation. When sufficient skill is obtained by dissection of these larger forms, smaller ones may be taken, and after a short time the student experiences but little more difficulty in dissecting a grasshopper or a snail than in a pigeon or turtle.

Besides obtaining a skill in dissection and a capacity for observation, a student is led in this anatomical course to make comparisons between the various objects dissected. This results in a recognition of similarities and differences, and exercises the reasoning faculties. The value of the mathematical sciences in logical training is often insisted upon, but to the writer it seems as if the biological sciences were even more important from this standpoint. In mathematics, given such and such premises, there can be but one conclusion; there is no alternative, while in zoölogical reasoning there is an element of uncertainty to be eliminated. Each fact observed must be weighed,