18 . OHIO STATE ACADEMY OF SCIENCE. 
Ill. A third method, mstead of taking an entire brain as 
the unit of research, concentrates attention upon a single fune- 
tional system and seeks to get exhaustive comparative knowledge 
of it in many types. Starting with a fairly accurate and detailed 
knowledge of the functional systems at the periphery, we have 
simply to extend the lines of inquiry here blocked out for us. 
This gives a type of problem which is much more approach- 
able than the others. It is not so complex, but more intensive. 
Of still more importance are the facts that the anatomical data 
can be directly correlated by physiological experimentation, and 
the method is open to experimental control all along the line. Our 
degeneration methods open up possibilities here which are incom- 
parably more valuable than the most precise anatomical observa- 
tion. 
And nature has performed for us a series of experiments 
which are in a sense the converse of our degeneration methods. 
The various sensori-motor systems are very unequally developed, 
some animals possessing one in a high state of elaboration, some 
another. If therefore we begin our studies on the visual system 
for instance, with animals such as most birds with very highly 
developed eyes, and then compare with animals with vestigeal 
eyes, it is evident that we have here a means of isolating the 
system for scientific study which has some points of superiority 
over artificial experimental methods. Fortunately within the 
group of fishes, whose brains are all constructed on a plan funda- 
mentally similar, we have the most remarkable diversity in the 
degree of development of the several systems, so that this is a 
favorable starting point for this method, especially since the brain 
is composed almost wholly of the simpler reflex mechanisms with- 
out the complications which we find in mammals due to the 
enormous developments of higher associational centers in the fore- 
brain. Some fishes have huge eyes, some are blind; some have 
elaborate olfactory apparatus, some very slight; some show a 
marvelous hypertrophy of the organs of taste, or touch, ete. 
These organs are all open to physiological study and so the fune- 
tions can be accurately determined. Then, having found the 
cerebral pathways for each system where it reaches its maximum 
development, we can more easily trace out the system in other 
types, and thus arrive ultimately at a full knowledge of its 
evolutionary history. 
All scientific method is both analytic and synthetic. In the 
phyletic type of neurological method, these two processes are apt 
to be far separated and the observed facts may remain inert and 
