30 BRAINS OF RATS AND MEN 



discharged nervous impulses from the organs of 

 muscle sense, the eyes, and ail other sense organs 

 which may serve postural adjustments and the 

 orientation of the body and its members in space. 

 These are the proprioceptive senses, and thus the cer- 

 ebellum was elaborated as the great central adjustor 

 of proprioceptive control. 



The indications are that the cerebellar cortex 

 is concerned more with the convergence and sum- 

 mation of diverse sensory impulses than with their 

 refined analysis and redistribution. Which particular 

 motor centers will receive the nervous impulses dis- 

 charged from the cerebellum is apparently deter- 

 mined less by what is going on in the cerebellum itself 

 than by what systems are in actual function in the 

 rest of the nervous system. In accordance with the 

 physiological principles of "drainage" and of "induc- 

 tion" (p. 59), the circuits acting in the brain stem tend 

 to capture and utilize the cerebellar discharge. All 

 this is in marked contrast with the cerebral cortex, 

 which is subdivided into very many structurally 

 diverse fields whose functions include the analysis 

 of sensory data, their regrouping, and the determina- 

 tion within the cortex itself of the particular motor 

 systems which are to be activated. 



The cerebellum emerged from the vestibular 

 nuclei. In its more highly elaborated forms its func- 

 tions are enlarged to include some sort of reflex con- 

 trol of all movements of skeletal muscles and of 



