AN ATTEMPT TO DEFINE THE PRIMITIVE 



FUNCTIONAL DIVISIONS OF THE CENTRAL 



NERVOUS SYSTEM. 



By J. B. Johnston. 



The time has come, as I think every comparative neurol- 

 ogist feels, that we must break away from the old cumbersome 

 nomenclature and descriptions imposed by human anatomy, 

 and create a new and simple mode of describing the brain which 

 shall express rather than obscure the functions of its several 

 parts. Any movement of this kind must be made with the 

 greatest care regarding the foundation in fact and also with due 

 care to avoid too great a gap between the old and the new. 

 Although the contribution offered here is based chiefly on the 

 author's investigation of the brain of fishes, full consideration 

 has been given to, the work of others, and many parts of the 

 following scheme have been suggested by one or another of 

 numerous investigators, of whom Gaskell, Strong, and Her- 

 RiCK may be named. 



The analysis l^y Strong (i8) of the cranial nerves into 

 components which serve similar peripheral organs and have the 

 same central endings, has given both stimulus and direction to 

 the most fruitful period in the study of the cranial nerves. This 

 work, which has been extended by Herrick (7, 8, 9), and 

 others, has also helped toward a better understanding of the 

 central system. The investigation of the sturgeon brain by the 

 present writer (12) led to the discovery of no less definite and 

 clearly marked divisions of the central system corresponding to 

 the components of the cranial nerves. The study of the brain 

 of Petromyzon (13) shows that it, too, falls strictly in line with 

 the brain of other fishes in this regard. The work of Houser 

 (10) on the selachian brain and the results of those students of 

 the cranial nerves who have investigated the internal relations 

 of the nerve components, are in accord with these results in 



