PROBLEM OF THE CEREBRAL CORTEX 27 



the distribution in space of nervous impulses from 

 diverse sources to diverse final common paths, with 

 preservation of the identity and anatomical separate- 

 ness of the several nervous circuits which are thus 

 compounded. This implies that this sort of apparatus 

 is concerned with refined analysis of many afferent 

 systems of different kinds and their regrouping and 

 redistribution through a wide range of efferent path- 

 ways. This type of analysis attains its maximum 

 efficiency in the human cerebral cortex. 



More elementary mass reflexes as we see them 

 executed in the human spinal cord and corpus 

 striatum do not require this elaborate switchboard 

 type of organization. Here all afferents, no matter 

 of how diverse sorts, discharge into a few final com- 

 mon paths, each of which innervates extensive sys- 

 tems of motor organs, and the adjusting mechanism 

 may be exceedingly simple, as will appear in the 

 account of the correlation centers in the next chapter. 



The relation of the cerebral cortex to these primi- 

 tive mass reflexes or total reactions of the body is a 

 very interesting but still unsolved problem. In some 

 cases the cortex seems to exert a trigger action, releas- 

 ing (or inhibiting) organized lower neuromotor sys- 

 tems which are already set for the performance of 

 locomotion or some similar elementary form of 

 response. 



This implies that in such cases the cortex acts as 

 a "decider," determining whether a particular reflex 



