198 BRAINS OF RATS AND MEN 



process of heavy traffic. The hnes of central trans- 

 mission have been transferred from the direct path 

 between sensory receptor and final common path {S- 

 Foi the figure) to a roundabout way {S-C-L-C'-F). 

 The details are unknown, but that something of this 

 sort takes place is highly probable. In this process of 

 facilitation there may be, and doubtless are, other 

 changes involved, some central and some peripheral; 

 but for our present purpose this central readjustment 

 may be taken as representative of them all. 



This is the learning process. It is an active change 

 in the internal organization or "set" of the neuromus- 

 cular apparatus. Now, the retention is nothing other 

 than the preservation, for longer or shorter time, of 

 this change in the **set" of the apparatus. As long as 

 this endures the "memory" is retained. No active 

 process, either psychological or physiological, is in- 

 volved. There is nothing about it more magical or 

 esoteric than there is in winding an alarm clock at 

 night in the assurance that when the hour-hand reach- 

 es six o'clock the spring will be released and the 

 alarm which has been "set" will react in the way prop- 

 er for all well-regulated alarm clocks. The recall is 

 simply the reactivation by an appropriate stimulus of 

 a mechanism which has through experience been so 

 "set" that it will react in some learned behavior pat- 

 tern when the appropriate trigger is pulled. 



As we have seen, this is not essentially a cortical 

 type of process, for it is perfectly exhibited by many 



