86 



K. S. L ASHLEY 



The total extent of the lesions is shown in figure 5. The entire 

 middle third of the dorsal surface of the cerebrum was covered. 

 The injuries on the lateral surfaces do not include all of the tem- 

 poral lobes. No one of the animals of this group required as 

 many trials for learning as the average of normals. 



The greatest extent of injury appeared in number 13 (plate II, 

 figure 13) and this animal learned more quickly than any of the 

 others. 



2000 



1500 



1000 



500 



fff 



20 



trials 



FIG. 6. A COMPARISON OF THE RATE OF LEARNING IN NORMAL ANIMALS AND IN 

 ANIMALS AFTER FRONTAL OPERATIONS 



The average time in seconds per trial is plotted. 

 Operated rats . From Lashley and Franz, '17. 



Normal rats: , 



Group 5. Frontal pole destroyed. In earlier work this area was 

 covered rather thoroughly by experiments on the inclined-plane 

 box. In that work six animals were trained on the inclined-plane 

 box after injury to the frontal pole of the cortex and their aver- 

 age rate of learning was compared with that of normals on the 

 same problem. The curves showing the rates of learning of these 

 two groups are reproduced in figure 6. The total extent of the 

 lesion in the six animals is shown in figure 7. There was no sig- 

 nificant difference between these groups (Lashley and Franz, '17). 



