CEREBKAL FUNCTION IN LEARNING 125 



innervation. The loss of voluntary movement in hemiplegia, s 

 pure motor aphasia, etc., might thus be due solely to the dis- 

 turbance of some fundamental coordinating mechanisms, upon / 

 which the habitual reactions are superimposed, rather than to 

 interruption of the habit-mechanisms themselves. -J 



Existing evidence of the motor function of the corpora striata 

 has been rather uncertain. Luciani ('15) and others have ob- 

 tained movements from stimulation of the caudate nucleus but 

 Von Bechterew ('09) claims that this was due to spread of current 

 and that no movements can be elicited if degeneration of the 

 internal capsule is first induced. The data given in section 

 VI seem to show the motor function of the striate nucleus 

 conclusively. 



With what justice may results on cerebral function found for 

 the rat be extended to higher forms? The rat has a very primi- 

 tive cerebral organization but I doubt that this justifies the as- 

 sumption that there is any fundamental difference in cerebral 

 mechanism between the rat and even man. The chief arguments 

 which have been advanced for the greater specialization of cere- 

 bral function in higher forms have been the lack of paralysis from 

 destruction of the motor cortex in animals below the primates, 

 rapid recovery from sensory defects after destruction of afferent 

 projection areas in lower forms, and the increasing number and 

 complexity of histologically distinct cortical areas with advance- 

 ment in the evolutionary scale. The significance of the last 

 point is questionable. The rat has many areas distinct in cyto- 

 architecture but these seem to have no absolute functional sig- 

 nificance. The data on the striate nuclei suggest that the motor 

 area is quite distinct hi the rat, but with a predominance of func- 

 tion hi the subcortical nuclei which is assumed by the motor cor- 

 tex in higher forms. As for the greater ^loss of sensory and in- 

 tellectual capacities and the slower recovery which appears after 

 cerebral injuries in higher forms, they are restricted largely to 

 man. The differences between the rat and the apes are scarcely 

 greater than those between the apes and man. Both the sen- 

 sory and intellectual capacities of the adult man are the result of 

 years of training which have led to the establishment of countless 



