SOURCES AND ENDS OF HUMAN EFFORT 335 



connections are such as to permit their activation in 

 relation with each one of numerous different associa- 

 tional patterns, thus making possible a great influx 

 of nervous energy in addition to that of the neurons 

 which form the essential links in the particular asso- 

 ciational chain at the moment active. 



These cortical reserves are drawn upon, not like 

 those of the lower brain centers to reinforce the ad- 

 ministrative machinery of structurally predetermined 

 reactions, but to co-operate in determining on the 

 basis of personal as well as racial experience what act 

 is appropriate to the present situation. This is a dis- 

 tinction of far-reaching importance. It is the presence 

 of the cortical reserves, partly unformed and mobile 

 and partly laid down as definite mnemonic patterns 

 or engrams, that make constructive thinking possible, 

 a process in which residua of former experience are 

 reassembled in new patterns. 



Now, colligated with the amplification of the 

 cortical apparatus for registering and reactivating the 

 mnemonic and other reserves of the human associa- 

 tional fields, we observe the elaboration of symbolic 

 thinking and the emergence of new capacities to 

 formulate uniformities of experience, to project these 

 uniformities into the future, and so to predict coming 

 events. 



This forward projicience of experience is not a new 

 and mystical "force" added from the outside to our 

 biological impulses to transform them into volun- 



