26o BRAINS OF RATS AND MEN 



(that of reptiles) develops simultaneously as three 

 sheets of superficial cells, each of which is related with 

 a different complex of subcortical correlation sys- 

 tems — hippocampal, pyriform, and general cortex. In 

 other words, there can be no cortex without some 

 degree of cortical localization of function. 



7. Primitively, cortical activity is invoked, not to 

 produce action, but within action, first checking in- 

 appropriate reflexes and then amplifying, redirect- 

 ing, recombining, or otherwise improving upon the 

 immediate responses which have already been ini- 

 tiated in the subcortical reflex centers. The primitive 

 cortex exerts a regulatory control upon behavior in 

 process. 



The cerebral cortex ordinarily is not activated by 

 simple uncomplicated nervous impulses coming in 

 directly from the periphery,' but it is called into play 

 by activities going on in the lower correlation centers 

 and it articulates with these as going concerns. Sense 

 impressions are received and combined in subcortical 

 centers, and there resolved into actually operating or 

 incipient motor responses before they can get through 

 to the cortex at all. The cortex is not reached by these 

 nervous impulses if the situation is one for which the 

 organization of the lower centers is adequate, that is, 

 if a standardized reaction of reflex or instinctive type 

 gives a satisfying result. Otherwise, collateral efferent 



*The anterior pyriform cortex is a conspicuous exception to this 

 rule, which is discussed on pp. 26, 86. 



