STUDIES OF CEREBRAL FUNCTION IN LEARNING. VII 45 



the mass action shown in these experiments is a general prin- 

 ciple of neural activity. 



Current doctrines of cerebral function, in so far as they 

 attempt to specify the mechanism of integration and are not 

 content with vague ascriptions of mental traits to anatomical 

 areas, are based upon the principle of reflex organization. 

 In its present form this conception implies the dependence 

 of reaction upon the connections of particular neurons. It 

 of course permits of innumerable complications through in- 

 hibition or facilitation exerted between reflex arcs, but the 

 principle remains that of absolute dependence of the reaction 

 upon the particular neurons which are activated. Direct 

 adaptive association between afferent and efferent paths can 

 only occur when low synaptic resistances already exist be- 

 tween them, established either by growth or learning proc- 

 esses. New coordinations can be established only by 'random' 

 activity and ' selection. ' 



The facts of mass action do not readily fit into such a 

 schema and in conjunction with the facts of temporal varia- 

 tion, equipotentiality, and the functional equivalence of final 

 common paths form a consistent body of physiological evi- 

 dence opposed to the reflex hypothesis. This, with behavior 

 problems of the type cited above, seems to demand a plas- 

 ticity of neural function which cannot be deduced from any 

 explanatory system dependent upon the connections of par- 

 ticulate neurons. As Herrick says, ''the concept of the reflex 

 is not a general master key competent to unlock all of the 

 secrets of brain and mind," and the inadequacy of the reflex 

 theory seems to demand the formulation of some additional 

 or alternative hypotheses. As yet, too little is known of 

 the non-conformable cases to permit of any detailed state- 

 ment. It must suffice at present to point out that the problem 

 raised for neural function has many points in common with 

 the problems of morphogenesis which arise in experimental 

 studies of embryology and regeneration. In both cases it is 

 the pattern or total relationship of parts as well as particu- 

 late structures which determines the final product. The best- 



