82 K. S. LASHLEY 



Number of trials required for learning 97 



Per cent of total cortex destroyed 17.8 



Lesion: Plate I, figure 8. The lesions of both hemispheres were con- 

 fined to the dorsal surface. The cerebellar surfaces of the cerebrum 

 were intact. The hippocampal lobes were uninjured. The lesions 

 extended laterad over the surfaces of the hippocampal lobes to the 

 level of the fourth ventricle. 



Number 9. Large male, about 200 days old. Both occipital lobes 

 were injured with the cautery as above. Recovery was normal. Train- 

 ing was begun 22 days after the operation. The animal seemed quite 

 normal in behavior, was aggressive and dominated the other males in 

 the cage with him. In the problem box his reactions were prompt and 

 the door was learned in six trails. 



Number of trials required for learning 46 



Per cent of total cortex destroyed 40.8 



Lesion: Plate I, figure 9. This animal showed the most extensive 

 destruction of any of the occipital cases. The lesions of both hemi- 

 spheres extended from the anterior edges of the hippocampal lobes cau- 

 dad and laterad to include all of the cortex dorsad and laterad to the 

 hippocampal lobes and all the posterior mesial surfaces except a small 

 area on the left hemisphere at the level of the thalamus. The hippo- 

 campal lobes seemed intact. 



Number 10. Small male, 102 days old. The occipital lobes were 

 injured with a scalpel. Recovery was rapid with no noticeable disturb- 

 ances of behavior. Training was begun 13 days after operation, be- 

 fore the animal had recovered his full strength. For the first two trials 

 he was allowed to remain in the problem box over night. Thereafter 

 his reactions were prompt. 



Number of trials required for learning 82 



Per cent of total cortex destroyed 20.3 



Lesion: Plate I, figure 10. On the right hemisphere the lesion ex- 

 tended over an area covering the dorsal and lateral surfaces of the hip- 

 pocampal lobe, narrowing as it passed laterad and ending at the level 

 of the fifth ventricle. The dorsal surface of the lobus hippocampus 

 was destroyed. The lesion on the left hemisphere was similar but less 

 extensive. 



