STUDIES OF CEREBRAL FUNCTION IN LEARNING. VII 



27 



in others are stippled. The areas which were destroyed in 

 every case are marked in solid black. Only the dorsal con- 

 vexity of the occipital region of both hemispheres was de- 

 stroyed in all. Consequently, this must be the focal point 

 implied in the foregoing hypothesis. But this area was also 

 completely destroyed in cases 55, 58, 59, 61, 62, 69, and 73, 

 none of which made more than two errors in retention tests. 

 This dorsal area alone cannot, therefore, have any special 

 significance for the visual function. 



All cases which made not more than five errors in retention 

 tests were selected and a composite diagram constructed of 



Text fig. 4 Composite diagram made my superimposing the lesions in animals 

 of group B which made more than thirty errors in retention tests. The areas in 

 solid black were destroyed in all cases. The stippled areas in some, but not all. 



the lesions in them, to determine if any possible visual area 

 uniformly escaped destruction. These were nos. 50, 51, 52, 

 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 66, 67, 69, 71, 72, 73, 77, 

 and 84. The total extent of the lesions in these cases is 

 shown in text figure 5. The combined lesions cover the entire 

 occipital third of the cortex with the exception of the extreme 

 lateral pole of the right hemisphere. In this series no possible 

 focal point could have escaped injury, and the fact that none 

 of the animals showed deterioration of the habit demonstrates 

 that no such point exists within the occipital region of the 

 cortex. 



