CEREBRAL FUNCTION IN LEARNING 123 



descending directly from other cortical regions. The problem 

 is an interesting one and can be readily tested by careful 

 operations. 



VII. THE SIGNIFICANCE OF THE GENERAL RESULTS FOR THE 

 CEREBRAL MECHANISM OF LEARNING 



The experiments recorded in this paper give no indication of 

 the character of the reintegration of conduction paths which oc- 

 curs in learning. That problem must wait for a physiological 

 analysis of the factors which determine the direction of conduc- 

 tion in the nervous system and for much more detailed studies of 

 the behavior of small groups of neurones in learning. But the 

 experiments do give some insight into the function of the anatomi- 

 cal divisions of the cerebrum in the acquirement and retention of 

 habits and the course of the conditioned-reflex arcs through 

 which learned reactions are mediated. 



The point most clearly demonstrated is the complete vicarious 

 functioning of all parts of the cerebrum in learning. Not only 

 are areas to which associative function might be ascribed unnec- 

 essary for the acquirement of habits but even projection areas, 

 which have been considered as hereditarily organized relay sta- 

 tions for impulses to or from the cortex, may be dispensed with 

 without any discoverable loss in ability to learn a difficult reac- 

 tion which is normally mediated by those areas. This capacity for 

 vicarious functioning seems to hold true both for the cortex and 

 for the underlying structures making up the archipallium. Such 

 a fact can only be explained by the assumption of a fan-like dis- 

 tribution of fibers from the lower centers to all parts of the cere- 

 brum, permitting incoming impulses to reach any part of the I 

 cortex, which happens to be intact, with equal ease. 



Yet if this is the case, it is not clear why any particular part 

 of the cortex should function to the exclusion of other parts in the 

 formation of a habit under normal conditions, unless we can 

 further assume a somewhat greater concentration of fibers from 

 given lower centers in given cerebral areas. Probably this rep- 

 resents the true state of affairs, for it is evident from the fact that 



