214 BRAINS OF RATS AND MEN 



tion of learned reactions is abolished. Upon removal 

 of the entire cortex the general tonic cortical effect is 

 abolished. The operation has not stimulated inhibi- 

 tory fibers, as some have supposed; it has removed the 

 sources of tonic activation which normally are always 

 operating. 



The experimental and the anatomical lines of evi- 

 dence converge in support of the conclusion that in 

 the rat the non-specific tonic action of the cortex 

 plays the major role, the specific phasic influence be- 

 ing relatively subordinate. The wide extent of the ex- 

 citable cortex, its incomplete differentiation from the 

 somesthetic cortex (which is presumably chiefly kines- 

 thetic in the rat) and from the underlying corpus stri- 

 atum, and the extirpation experiments all agree in 

 substantiating Lashley's belief that in the rat "it is 

 probable that the stimulable cortex and the corpora 

 striata have alternative motor functions" (1920, p. 

 126) and that the leading function both of the excit- 

 able cortex and of the residual 50 per cent (more or 

 less) of cortex after partial decortication is to supply 

 a substratum of faciHtating impulses of postural and 

 tonic character (1924, pp. 274, 275). 



In man the relative importance of phasic and tonic 

 influence of the cortex upon behavior is probably re- 

 versed. One can agree with Lashley (1920, p. 125), 

 ''The rat has very primitive cerebral organization but 

 I doubt that this justifies the assumption that there 

 is any fundamental difference in cerebral mechanism 



