CEREBEAL FUNCTION IN LEARNING 85 



a stereotyped reaction to the second platform which delayed learning 

 considerably. 



Number of trials required for learning 99 



Per cent of total cortex destroyed 24.3 



Lesion: Plate II, figure 14. On the dorsal surface of both hemi- 

 spheres the lesion extended from the knee of the corpus callosum to the 

 middle of the hippocampal lobes. On the right hemisphere it narrowed 

 laterad, extending over the surface of the hippocampus. On the left 

 hemisphere the lesion involved the same areas and in addition most of 

 the cortex overlying the corpus striatum was destroyed. The lower 

 nuclei seemed to be uninjured. 



Number 15. Small female, 70 days old. The parietal areas were 

 cauterized as in the case of number 14. Recovery was slow and the 





FIG. 5. THE TOTAL EXTENT OP THE LESIONS IN ANIMALS OP GROUP 4 AFTER 

 OPERATIONS IN THE PARIETAL REGION 



animal was still weak at the beginning of training. Reactions were 

 prompt from the first and learning progressed normally. 



Number of trials required for learning 78 



Per cent of total cortex destroyed 14.2 



Lesion: Plate II, figure 15. The lesions on both hemispheres were 

 confined to small areas lying above the lateral ventricals and corpora 

 striata. Subcortical structures were uninjured. 



The results of these tests are summarized in table 2. The 

 maximum number of trials required by any member of the group 

 was 101 (11). The smallest number was 41 (13). The average 

 number of trials is 80. The average time required per trial on 

 successive days' training is shown in table 3. 



