

98 K. S. LASHLEY 



Number 6. Complete destruction of the left C. S. 

 Number 13. Superficial injury to the right C. S. 

 Number 19. Severe injury to the left C. S., slight injury to 

 the right. 



The average number of trials required for learning by these 

 animals was 53.0 which is slightly less than the average of 

 paretic animals (most of them were paretic). The corpora 

 \ striata are not of greater importance for learning than other parts 

 of the cortex. 



It has been claimed that injury to the corpus callosum results 



in some deterioration. Since the experiments have shown that 



the destruction of an entire hemisphere does not retard learning, 



the interruption of comimssural fibers can hardly have a different 



effect. Actual test of this is provided by annuals number 11, 



14, and 18 which showed a very nearly complete destruction of the 



f corpus callosum with cysts exposing the lateral ventricles. The 



I average number of trials required for learning by these three 



I annuals was 83.6, which is not significantly greater than the 



(^ average of all. 



These records show that the structures mentioned have no 

 special function in learning. In the various tests practically every 

 deep-lying structure above the thalamus was injured and it seems 

 clear that none of the cerebral nuclei is of any greater importance 

 for learning than is the pallium. 



IV. THE RELATION OF THE RATE OF LEARNING TO THE AMOUNT OF 



CEREBRAL INJURY 



The apparent superiority of the operated animals in the fore- 

 going experiment raises again the question of the real significance 

 of the data obtained with the double-platform box and with the 

 inclined-plane box in earlier work. Further evidence upon the 

 / point is furnished by a study of the relation of the rate of learning 

 - to the amount of cerebral material removed. This relation is of 

 ^considerable interest from other standpoints also. If, as seems 

 to be the case, there is no specialization of cerebral function for 

 the acquirement of habits, learning may be the result either of 



