106 K. S. LASHLEY AND S. I. FRANZ 



tidty and by a complete loss of the motor habit. The habit was 

 reacquired with, normal rapidity at first but a normal degree of 

 proficiency was not attained. 



Experiment 28. The frontal poles of the cortex were destroyed 

 in a large male, 140 days old. He had been trained on the in- 

 clined-plane box for 30 trials. The average time per trial was for 

 the first five trials: to plane, 2594 seconds; to door 224. That 

 for the last five trials was: to plane, 22.0 seconds; to door, 1.6 

 seconds. 



Retention was tested on the day following the operation but 

 no approach to normal activity was obtained until the third 

 day. He then tripped the plane three times, requiring an aver- 

 age time of: to plane, 493 seconds; to door, 79 seconds. For 

 the following week he did not get upon the food box in a total 

 of six hours spent in the restraining cage. He then became 

 active again and eventually learned the problem, requiring 

 about the same time as in the initial practice to reduce his aver- 

 age' time to less than 30 seconds. In the early trials of the re- 

 tention tests there was no uniformity in the method of tripping 

 the plane and there was never any indication of the retention of 

 a specific habit of reaction. 



Lesion (plate III, fig. 28). Right hemisphere. There is a 

 lesion of the dorsal convexity over the gyrus hippocampus and 

 extending forward around the anterior surface of the hippocam- 

 pus, along the roof of the lateral ventricle and ventrad in front 

 of the knee of the corpus callosum through the peduncle, sever- 

 ing the frontal pole. The entire lobe in front of the corpus 

 striatum is degenerated and filled by a large cyst. 



Left hemisphere. The lesion is similar to that on the right, 

 but extends farther back along the external capsule, with de- 

 generation of a part of the orbital cortex. Only the outer half 

 of the peduncle is injured so that the mesial surface of the lobe 

 is probably functional. 



After almost total destruction of both anterior poles of the cortex 

 in front of the corpora striata this animal completely lost the habit 

 of the inclined-plane box, but acquired it again in about the same 

 time as was required for initial learning. 



