22 BRAINS OF RATS AND MEN 



types of cortex, but there are from the start very 

 fundamental differences between them, and in their 

 more highly elaborated forms they diverge widely in 

 structure and physiological action. The technique 

 and the results of their action in some respects are so 

 unlike that their significance in behavior is as different 

 as two nervous organs can well be. 



The cerebellum controls (always unconsciously) 

 the co-ordinated action of various parts of the body 

 under the influence, chiefly, of stimuli arising within 

 the body (semicircular canals, organs of muscle sense, 

 etc.). The cerebral cortex, on the contrary, exerts its 

 influence primarily in relation to responses to external 

 stimuli (exteroceptive reactions) and, in its higher 

 forms at least, occupies a dominant position in the 

 apparatus of intentional control of behavior. 



This difference is neurologically, physiologically, 

 psychologically, and sociologically of fundamental 

 significance. For the survival of any organism, 

 whether dogfish or business man, depends first upon 

 his ability (consciously or unconsciously) to adjust 

 his behavior to the environment in which he must 

 live — the exteroceptive reactions — and in the second 

 place to execute a course of action whose end or 

 objective has already been determined with speed, 

 precision, and vigor — and this is fundamentally a 

 proprioceptive reaction. 



The proprioceptive activities are of necessity very 

 rapid immediate responses to momentarily changing 



