386 C. JUDSON HERRICK 



Thus each primary bulbar center reached by terminals of root 

 fibers is to some extent also a correlation center and the analysis 

 of function hi the reactions is still incomplete. 



In the mammals the functional differentiation of the primary 

 bulbar centers is complete and the functions of correlation are 

 transferred to higher cerebral centers. Simpler total reactions 

 of the more primitive sort are, however, still provided for in the 

 formatio reticularis of these higher brains. 



The examination of the series of types of reflex pattern now 

 known in Amblystoma suggests the dominance of the integrative 

 function of the vertebrate central nervous system from its earliest 

 phylogenetic phases. The simplest responses to external stimu- 

 lation, such as the avoiding reaction and the swimming reflex of 

 very young larvae (Coghill), are simple total reactions involving 

 the coordinated action of large masses of body musculature. 

 Within such a unitary reflex system, which necessarily requires the 

 orderly participation of extensive regions of the nervous system, 

 more refined special movements may be differentiated, and this 

 involves the segregation of particular functional areas within the 

 originally unitary system under the influence of the progressive 

 differentiation of the receptor and effector apparatuses. 



Throughout this process of differentiation the correlation 

 centers, as they become more individualized from the primary 

 unitary system, are pushed farther and farther back from the 

 periphei'y ; but at no stage in the process is the primitive dominance 

 of the integrative function of the system as a whole lost. The 

 preservation of the functional integrity of the individual during 

 the process of differentiation of its parts is the most important 

 function of the higher correlation centers, as Sherrington has so 

 graphically shown. 



LITERATURE CITED 



Beccari, N. 1907 Richerche suUe cellule e fibre del Mauthner e suUe loro con- 

 nessioni in pesci ed anfibii (Salmo f ario, S. irideus e Salamandrina per- 

 spicillata). Arch. di. Anat. e di Embriol., vol. 6. 



Coghill, G. E. 1901 The rami of the fifth nerve in Amphibia. Jour. Comp. 

 Neur., vol. 11, pp. 48-59. 



1902 The cranial nerves of Amblystoma tigrinum. Jour. Comp. Neur., 

 . vol. 12, pp. 205-289. 



