264 BRAINS OF RATS AND MEN 



previous allied reactions. The efficiency of this latter 

 process is dependent upon the mass of the cortex itself 

 and the nature of its internal organization. It is pres- 

 ent (so far as evidence now goes) in an exceedingly 

 generalized form, if at all, in reptiles and lower mam- 

 mals. The ability to retain such organic memories of 

 complex individual experiences (as contrasted with 

 those acquired by the more tedious trial-and-error 

 method) seems to be correlated with the presence of 

 highly developed associational tissue outside of the 

 cortical projection centers, this culminating in the hu- 

 man brain. 



These mnemonic functions of the human cerebral 

 cortex are perhaps its most distinctive properties up- 

 on which depend all the nobler human faculties. In 

 situations where the immediate responses of the in- 

 nate reflex and instinctive apparatus of the brain stem 

 prove inadequate to determine the appropriate re- 

 sponse or where these simpler systems interfere so as 

 to inhibit all reaction, there is stasis and summation in 

 the lower centers, the longer cortical arcs are acti- 

 vated, mnemonic traces of previous allied reactions 

 here laid down are quickened, and the dilemma is 

 resolved in the light of former experience. 



It is not to be assumed that the memories to which 

 reference is here made are psychological images, 

 mythical subconscious entities, or so-called uncon- 

 scious mind. Just what the mechanism is we do not 

 know, but the assumption that best fits the observed 



