CEREBRAL FUNCTION IN LEARNING 89 



Lesion: Plate II, figure 18. On the right hemisphere a transverse 

 cut completely separated from the rest of the brain all of the cortex 

 lying above the corpus callosum, from the anterior border of the hippo- 

 campus to the olfactory fibers at the base of the frontal pole. The 

 latter are uninjured, as are the subcortical nuclei. The lesion of the 

 left hemisphere is similar to that on the right, except that it extends 

 caudad to the middle of the hippocampal lobe. 



Number 19. Medium sized female, about 150 days old. The opera- 

 tion was similar to that in the case of number 18. The animal devel- 

 oped a slight right paresis which persisted throughout the experiments. 

 Training was begun 22 days after operation. 



Number of trials required for learning 27 



Per cent of total cortex destroyed 31.9 



FIG. 8. THE TOTAL EXTENT OF THE LESIONS IN ANIMALS OF GROUP 6 AFTER 

 OPERATIONS ON THE FRONTAL AND PARIETAL REGIONS 



Lesion: Plate II, figure 19. On the right hemisphere the lesion in- 

 volved the cortex overlying the corpus striatum and the lateral surface 

 of the frontal pole, to the level of the lateral ventricle. On the left, 

 the lesion included the cortex overlying the corpus striatum, and the 

 latter was also destroyed. The remaining cortex was not degenerated, 

 but the section clearly passed entirely across the frontal pole through 

 the corpora striata and the septum lucidum, and the inclusion in the 

 lesion of all the cortex cephalad to this seems justified. 



The records of these animals are included in table 2. The 

 greater number of trials required is 51 (18), the lesser number is 

 27 (19). The average is 39. The average time required per 

 trial on successive days' training is shown in table 3. 



The total extent of the lesions is shown in figure 8. The entire 

 stimulable area and the entire frontal pole were eliminated with- 



