STUDIES OF CEREBRAL FUNCTION IN" LEARNING. VII 



23 



no greater than those of the lesser operations in the present 

 series (average 33.3 trials, 6.9 errors for relearning). It 

 seems, then, that differences in the general shock effects of 

 the operation are inadequate to account for the correlations 

 found. A further argument against general shock may be 

 derived from group A in which training was begun at the 

 same interval after operation as in group B, without the 

 slightest effect of the operation upon the rate of initial 

 learning. 



2. A diaschisis effect or specific depression of lower visual 

 centers requiring time for spontaneous recovery proportional 



Text fig. 2 Composite diagram made by superimposing the diagrams of the 

 lesions in cases 50 to 98, group B, showing the total range of the injuries in this 

 series. 



to the extent of the injury might result in a failure of animals 

 with extensive lesions to show retention, because the interval 

 between insult and retention tests was insufficient to allow of 

 recovery from the severer depression. To control this possi- 

 bility, the experiment with group C was undertaken. The 

 method w^ith this group was precisely the same as that with 

 group B, except that fourteen days were allowed to intervene 

 between training and preliminary retention tests and between 

 operation and postoperative tests. The data for group C are 

 summarized in table 4 and the lesions are shown in figures 

 103 to 112. The average extent of lesion for the group was 



