THEORY OF NERVE COMPONENTS. ^ 



It has now become a commonplace in science that all 

 parts of the nervous mechanism are so intimately inter- 

 woven and interdependent that the study of the functions 

 of the lower parts of the human nervous system is indis- 

 pensable for a correct comprehension of the higher spheres 

 of the brain. 



Our aim in this paper is to lead up to the solution of 

 the functions and structure of the cranial nerves and their 

 intra-axial continuations not only in the lower and higher 

 vertebrates but also in man. With a few notable excep- 

 tions, anatomists of the human nervous system have failed 

 to bridge over the gap between their own field and that 

 of the comparative neurologists, especially as to a compre- 

 hensive study of cranial nerve morphology and physi- 

 ology. The same may be said of the comparative neu- 

 rologists. Hence the subject is full of confusion. Our 

 aim is to bridge over this gap and ultimately not only to 

 contribute to the knowledge of the human nervous system 

 in particular, but also to work out some of the general laws 

 of structure and function of the nervous system in general. 



Let us now, although in an introductory manner, con- 

 sider more specifically the advantages of comparative neu- 

 rology as a method of research and some of its bearings 

 upon our problem of the phylogenesis of the cranial 

 nerve components. 



II. — Introductory Sketch of the Theory of Nerve Components. 



One of the most striking of the recent neurological 

 findings has been the discovery of the history of the 

 cerebral cortex. Starting from the fish types, in some of 

 which the pallium is a simple non-nervous membrane, it 

 is interesting to watch the emergence of the cortex and 

 parallel with it the progressive advance in psychomotor 



