266 BRAINS OF RATS AND MEN 



been made which preserve the effects of particular 

 patterns of associational activity — that is, better 

 memory — and (2) greater mobility of the elements so 

 that residual effects of previous cortical associations 

 can be recombined in new patterns with greater 

 facility — that is, better learning power. These two 

 functions are, of course, mutually interdependent. 



12. The dynamogenic influence of the cortex 

 which seems to play a dominant role in rats and simi- 

 lar lower types becomes not less but more important 

 in higher forms. But its character changes radically 

 with the elaboration of the intrinsic apparatus of 

 cortical association. As already mentioned, the non- 

 specific or generalized tonic influence seems to be 

 exerted in part by the corpus striatum and in part it 

 is preserved in the extensive extrapyramidal systems 

 of fibers which descend from the cortex to motor cen- 

 ters of the brain stem. Within the cortex a quite dif- 

 ferent apparatus of energy reserves is built up, which 

 comes to expression in behavior as a phasic (not 

 tonic) control of intentional behavior. The impor- 

 tance of this theme is so great that it will be treated 

 more at length in a later chapter dealing with the 

 vital reserves. 



In the preceding analysis the attempt has been 

 made to present generally accepted facts as observed, 

 supplemented in some cases where observed evidence 

 is meager by inferences which seem congruous with 

 the known facts. But probably few of these proposi- 



