122 BRAINS OF RATS AND MEN 



be noted that the effects here mentioned result from 

 destructive lesions of the striatum, releasing other 

 centers from striatal control. 



This conception of striatal functions in higher 

 mammals appears to be in marked contrast with the 

 conditions in birds and also in marsupials. Apparent- 

 ly, in higher mammals progressively more of the 

 phasic striatal functions are transferred to the cortex, 

 and the striatum becomes more and more an ancillary 

 mechanism to cortically originated acts. It is signifi- 

 cant that in so lowly an animal as the mouse Cajal 

 found collaterals from pyramidal tract fibers entering 

 the corpus striatum. 



That the cortex does exercise a real physiological 

 control over mesencephalic and still lower centers is 

 shown by experiments of Graham Brown (cited by 

 Wilson) that postural after-discharge activity from 

 mesencephalic stimulation is immediately wiped out 

 by stimulation of the pyramidal tract. "Non-postural 

 cerebral activity seems to abolish postural midbrain 

 activity." In lower mammals the cortex may have a 

 similar relation to striatal activity; in higher mam- 

 mals the striatum seems incapable of initiating even 

 postural activity without cortical participation (in 

 the normal). 



We conclude that parallel with the elaboration of 

 the cortex, and particularly of the motor cortex and 

 pyramidal tract, there is a progressive change in the 

 functions served by the corpus striatum; many of 



