REPORT OF THIRTEENTH ANNUAL MEETING. I7 



It is a general rule that in the body the components tend 

 to be distributed among a large number of nerves in a more or 

 less segmental way, while in the head they tend to be concen- 

 trated into a few pathways, or only one, into the brain, an adap- 

 tation which presents obvious advantages for the simplification 

 and unification of the secondary reflex paths from these primar\ 

 centers. 



Now, the central nervous system is, as we have already seen, 

 primarily a mechanism to facihtate the reaction of the animal 

 to impressions from without, in other words, to put the body in 

 correspondence with the environment. Its structure is directly 

 determined by the avenues of sense through which these stimuli 

 come in and by the character of the responses to these stimuli 

 which are necessary for the conservation of the organism. In 

 view of the fact that we already possess a detailed knowledge of 

 these peripheral nervous pathways, it is manifest that we have here 

 a most favorable avenue of approach in an analysis of the incon- 

 ceivable complexity of cerebral structure. 



We must know in detail the possible reflex pathways in the 

 brain for all olfactory, visual, gustatory responses, etc., in the 

 vertebrate type, and then on the basis of such a functional sub- 

 division of the brain the problem of the mechanisms of higher 

 cerebral processes may be attacked with a reasonable hope of suc- 

 cess. The investigation of the internal organization of the brain 

 may be pursued in several ways : 



I. The direct study of the human brain, both normal and 

 pathological. On account of the enormous practical importance 

 of neurology to both human psychology and pathology, research 

 naturally turned directly to the human brain ; but a more unfavor- 

 able starting point could not be found. 



II. It is now generally recognized that the complex human 

 brain can best be understood by finding first a simpler pattern 

 such as is presented by one of the lowest vertebrates. Accord- 

 ingly the phyletic method has dominated all recent neurological 

 research. The brains of individual species are studied and mono- 

 graphed, particular attention being paid to the lower members of 

 the vertebrate series in the hope of finding in them a schema or 

 paradigm which can be followed upward through the comparative 

 anatomical series and, after comparison with the ontogeny of 

 higher brains, lead to a reconstruction of the phylogenetic history 

 of the brain. While this method has been of great service, espe- 

 cially to such problems as can be approached from the study of 

 external morphology, it is immensely difficult when applied to the 

 histological problems, and as a matter of fact has not as yet taken 

 us very far. 



