CEREBRAL FUNCTION IN THE RAT 109 



from above the gyms hippocampus, through the anterior end 

 of the fornix and the corpus striatum to the base of the olfactory 

 bulb, completely severing the anterior pole. 



Both corpora striata were injured but show no sign of degen- 

 eration except along the edges of the cut. 



With almost complete destruction of the frontal poles of both 

 hemispheres and a probable degeneration of much of the cortex on 

 the orbital and occipital regions of the right hemisphere this animal 

 showed a complete loss of the habit and a failure to relearn the 

 problem. 



Experiment 31. The frontal poles of both hemispheres were 

 incised in a small female rat, 148 days old. She had been given 

 100 trials on the inclined-plane box, requiring as an average time 

 per trial for the first five trials: to plane, 591 seconds; to door, 

 67 seconds. For the last five trials these averages were : to plane, 

 5.4 seconds; to door, 3.2 seconds. 



Retention was tested on the second day after the operation. 

 The animal was very weak, but ran about actively in the re- 

 straining cage and twice crossed the plane without giving any 

 specific reaction to it. On the following day she spent thirty 

 minutes climbing up to the top of the restraining cage and fall- 

 ing back to the floor. She ran across the top of the food box 

 several times and in each case pitched off on her head without 

 making any attempts to catch the side of the box. For the 

 next two days her activity in the restraining cage was greater 

 than that of a normal rat, but was restricted wholly to attempts 

 to climb around the sides of the restraining cage just below the 

 top, with repeated heavy falls. On the sixth day after the op- 

 eration she died. 



Lesion. The brain of this animal was lost. 



Experiment 32. The frontal pole of the cerebrum was tran- 

 sected through two large trephine holes in the parietal region 

 of a small female rat, 146 days old. She had been trained on 

 the inclined-plane box for 55 trials. The average time per trial 

 for the first five trials was: to plane, 945 seconds; to door, 145 

 seconds. That for the last five trials was: to plane, 7.2 seconds; 

 to door, 2.6 seconds. 



