OHIO STATE ACADEMY OF SCIENCE. 



III. A third method, instead of taking an entire brain as 

 the unit of research, concentrates attention upon a single func- 

 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, etc. 

 These organs are all open to physiological study and so the func- 

 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 



