21 6 BRAINS OF RATS AND MEN 



And again: 



The statement that every act of the intact organism in- 

 volves the participation of every neuron within the central ner- 

 vous system is probably no more of an exaggeration than are 

 the extreme theories of precise localization of function or of 

 isolated conditioned reflex paths. 



The appeals here made to cortical reserves and 

 latent or potential nervous energies may seem to some 

 to be vague or even mystical veils for ignorance of ac- 

 tual organization. But the evidence, both anatomical 

 and physiological, upon which these references rest 

 is adequate. True, our knowledge of details is meager, 

 but the general mechanisms available are known suf- 

 ficiently for our purpose. This theme will not be 

 elaborated here, for the significance of cortical re- 

 serves in behavior will later be discussed in detail. I 

 wish to point out now, however, that this conception 

 of the dynamogenic role of the cortex in trial-and- 

 error learning by the rat seems to be in general accord 

 with Lashley*s view of cortical function as 1 under- 

 stand it (1922, p. 65; 1924, p. 272; 1926), though we 

 would perhaps work it out in detail differently. 



In summary, we find the clearest evidence for cor- 

 tical participation in the rat's learning by trial-and- 

 error. In some of its aspects this participation is defi- 

 nitely localized in specific regions, this localization be- 

 ing dependent primarily upon the topographic dis- 

 tribution of particular systems of thalamo-cortical 

 sensory projection fibers. There is also evidence 



