3i6 BRAINS OF RATS AND MEN 



stages have been so minutely recorded by Tracy. The 

 tonic influences of the cortex seem to be well ad- 

 vanced in differentiation before its phasic activities 

 have passed beyond rudimentary form (p. 213). With 

 further elaboration of the association centers as ap- 

 paratus of intentional control, the phasic activities of 

 the cortex "capture" and bridle the tonic influences, 

 and voluntary activity now directs the course of con- 

 duct which hitherto was under much more immediate 

 control of the exteroceptors. 



Trigger actions of the sort implied in immediate 

 response to stimulation, however complicated, are of 

 rather primitive physiological type. Opposed to them 

 is another kind of accumulation and expenditure of 

 reserves that is especially characteristic of the human 

 cerebral cortex. I refer to the preservation of some 

 sort of record of specific reaction patterns or experi- 

 ences which can on occasion be reactivated in the 

 original form. 



This, again, is a common protoplasmic function in 

 its elementary form. Even in higher animals habit 

 formation through repetition and learning by trial- 

 and-error do not seem to be essentially cortical types 

 of activity. But the retention of the effects of an in- 

 dividual experience in such form that the reacting 

 mechanism can later be reactivated with recall of the 

 experience and the interweaving of this recalled ex- 

 perience into a present reaction pattern, that is, the 

 influence upon present conduct of memories of partic- 



