98 K. S. LASHLEY AND S. I. FRANZ 



the corpus callosum to the external capsule and downward to 

 the floor of the ventricle. It probably involves very little de- 

 struction. There is also a lesion extending into the mesial cortex 

 just back of the knee of the corpus callosum, destroying a small 

 area. There is a partly absorbed clot in the third ventricle. 



In this animal three-fourths of the cortex on one frontal pole and 

 about one-eighth on the other were destroyed. The habit was partly 

 retained. The reactions after the operation resembled those ap- 

 pearing in the early stages of learning before a stereotyped mode 

 of solving the problem has been acquired. 



Experiment 22. Transverse incisions were made in the frontal 

 areas of the cortex of a large male, 140 days old, through two 

 trephine holes in the temporal regions. The animal had been 

 trained for 40 trials on the inclined plane box. The average 

 time per trial required for the first five trials of training was: 

 to plane, 330 seconds; to door, 38 seconds. The average time 

 per trial for the last five trials was: to plane, 6.6 seconds; to 

 door, 3.2 seconds. 



Retention was tested on the day following the operation but 

 the animal was stuporous and did not attempt to climb upon 

 the food box. On the third day he climbed upon the box but 

 got down immediately and remained quiet in a corner for 20 

 minutes. On the fourth day after the operation he climbed on 

 the box and fell off, striking the back of his head and lying stunned 

 for 30 seconds. When he recovered he climbed up on the box, 

 walked out on the plane from the rear and then went directly to 

 the food. The remaining trials were made quickly. The average 

 time for the first five trials, exclusive of the one in which the fall 

 occurred was: to plane, 45 seconds; to door, 5.6 seconds. The 

 tests were continued for 30 trials, which are compared with the 

 first practice series in figure 10. In the first tests he made fre- 

 quent trips from the plane to the door and made few pauses at 

 other parts of the restraining cage. In later practice he acquired 

 the habit of jumping up from the door to the back of the plane, 

 then walking out to the free end of the plane. This was 

 not the most frequent method that he had employed during 

 learning. 



