88 K. S. LASHLEY 



Lesion: Plate II, figure 16 (17). The lesion was identical in every 

 respect with that of number 16, except that the olfactory tracts were 

 severed, and as the figures for the two brains were practically indistin- 

 guishable, only that for number 16 is included in the plate. 



One of these two animals learned in normal time, the other 

 failed to learn the problem. The latter is particularly interest- 

 ing since she is the only animal of the series that failed. Her 

 brain was examined with especial care, but no injury could be 

 found that would account for the inability to learn the problem. 

 The section of the olfactory tracts will not account for the failure, 

 since, as was brought out in the protocol, she learned the second 

 platform very quickly. In all other respects the lesion was so 

 nearly identical with that of number 16, that the sections could 

 scarcely be distinguished. The animal was ill throughout the 

 experiment and this fact probably accounts for her behavior. 



Number 16 learned in normal time after destruction of 15.5 

 per cent of the cortex, in the region of the frontal pole. The ob- 

 ject of the tests was simply to check up the previous observa- 

 tions and a single positive case of learning is sufficient for this. 

 The double-platform box, as well as the simpler inclined-plane 

 box may be learned in the complete absence of the frontal pole 

 of the cerebrum. 



Group 6. Frontal and parietal areas destroyed. The object of 

 these operations was to destroy a very large area in the frontal 

 region, including all of the stimulable area. In this respect they 

 were successful, although the lesions were less extensive than I 

 had intended. They include from 24 to 31 per cent of the entire 

 cortex. Descriptions of individual tests follow. 



Number 18. Small male, about 150 days old. Large openings were 

 made in the skull over the parietal regions and an attempt was made to 

 destroy all of the frontal and parietal area through these. The animal 

 recovered rapidly, but was very wild and savage for some time after 

 training was begun, 38 days after operation. 



Number of trials required for learning 51 



Per cent of total cortex destroyed 24.9 



