36 Bulletin of Laboratoties of Dcnison University [Voi. xiii 



The labors of the students of nerve components have given 

 us for the peripheral nervous system a paradigm or schema 

 which seems to hold for all vertebrates, though with infinite 

 variation in its details ; and it now remains to correlate these 

 peripheral components with the central conduction paths so as 

 to give a detailed knowledge of the whole course of each reflex 

 pathway. 



In attacking this general problem there are obviously two 

 general lines of procedure open to us: — (i) beginning with 

 the simplest brains we may work out exhaustively for each 

 critical species in the phylogenetic series the conduction paths 

 as completely as possible by monographic treatment of types 

 and thus in the end approximxate to a reconstruction of the 

 phyletic history of the nervous system. (2) Or we may take 

 each sensori-motor reflex system as the unit and trace its 

 phylogeny through the series of types. This second method 

 has the obvious advantage that one can start with the system 

 in question in some type where it attains maximum develop- 

 ment and, having arrived at a thorough knowledge of its anato- 

 my and physiology here, it will be easier to read this schema 

 backwards to the more primitive animals, as well as forwards in 

 its further evolutionary modifications. It is hardly necessary 

 to call attention to the fact that the human nervous system is 

 the least favorable starting point for this sort of a research ex- 

 cept for the neo-pallium and its appendages. 



Each method has its advantages. The monographic treat- 

 ment of type brains is really far more difficult, even in the low- 

 est vertebrates, because of the difficulty in interpreting such 

 simple undifferentiated pictures and analyzing a complex where 

 there are few salient features. But nature has effected the 

 analysis for us in some of the more specialized types by the 

 hypertrophy of isolated systems ; and if, as sometimes happens, 

 the other functional systems are in a primitive or reduced con- 

 dition, we have a favorable point of approach for a monographic 

 study of the exaggerated functional system (cf Judson Her- 

 RiCK, '03). 



The purpose of this study is to make such a detailed analy- 



