Editorial. 1 69 



able fully to enter into their own data. Already some dozen 

 researches have appeared in this country largely inspired by 

 this point of view, which has, however, been generally ignored 

 abroad save for the admirable studies of Cole of Liverpool. 



We may, then, claim for the doctrine of nerve components 

 as comparatively studied that it is distinctly an American con- 

 tribution to neurological science. It is not necessary in this 

 place to enter into an exposition of what that doctrine is, for 

 this has been done in extenso in the address printed in our issue 

 for last December. What we wish here to emphasize is that, 

 apart from its great morphological value in determining 

 homologies and critically defining the proper use of the cranial 

 nerves in attacking such problems as the segmentation of the 

 vertebrate head and its relation to the trunk, etc., perhaps its 

 chief interest and value lie in the fact that it opens a very at- 

 tractive avenue for the study of the physiological subdivision 

 and interpretation of the entire nervous system, both central 

 and peripheral. 



In fact the whole point of this series of researches from 

 the beginning has been the accurate demarcation of functional 

 systems of neurones as the real units of the nervous system. 

 Starting at the periphery where the functions of the terminal 

 organs of the nerves are either well known or open to direct 

 experimental determination, the conduction pathway is followed 

 proximally into the brain and through its devious ramifications 

 within that organ. Ultimately when each such functional sys- 

 tem is exhaustively known we shall have the anatomy and 

 physiology of the central, as well as the peripheral, nervous 

 system well outlined and, when this knowledge is made com- 

 parative, the materials for a complete phylogeny of the nervous 

 system. 



The great problems of evolution, when finally solved, 

 must be stated in functional terms. It is the problem of evolu- 

 tion to determine not merely what has been the history of the 

 structural metamorphosis of organs and species, but what have 

 been the dynamic factors which have shaped that metamorphosis, 

 what influences of environment and internal organization have 



