92 K. S. LASHLEY AND S. I. FRANZ 



Temporal lobes destroyed 



Experiment 18. A large opening, 2 by 5 mm. was made on 

 each side of the skull just back of the front o-parietal suture of 

 a medium sized female rat, 140 days old. Through these the 

 scalpel was passed to destroy the temporal lobes. The animal 

 had been trained on the inclined-plane box for 115 trials. The 

 average time per trial for the first five trials was: to plane, 2719 

 seconds; to door, 61 seconds. That for the last five trials was: 

 to plane, 34 seconds; to door, 2.2 seconds. 



Retention was tested on the second day after the operation, 

 when the animal was active and in good condition. The aver- 

 age time for the nine trials given on this day was: to plane, 22 

 seconds ; to door, 1 1 seconds. Her specific reactions were wholly 

 confined to the plane and door. On different trials she ap- 

 proached the plane from different directions, but always tripped 

 it in the same way, by pushing down on its outer ^end with her 

 fore feet, and in every trial except the first she went directly 

 from the plane to the door of the food-box. 



Extent of lesions (plate III, fig. 18). Right hemisphere. 

 There is a large lesion on the dorsal convexity including almost 

 all the cortex dorsal and lateral to the gyrus hippocampus, ex- 

 tending from near the longitudinal fissure, over the convexity 

 and down over the temporal lobe to the level of the posterior 

 horn of the lateral ventricle, following the course of the external 

 capsule. 



Left hemisphere. The lesion on the dorsal convexity is simi- 

 lar to that on the right. It extends downward around the 

 antero-lateral face of the gyrus hippocampus and thence for- 

 ward through the lateral face of the corpus striatum. 



After a bilateral lesion destroying most of the cortex lying dorsad 

 and laterad to the gyri hippocampi the motor habit previously 

 established was retained. 



Experiment 19. In the skull of a small female, 148 days old, 

 two trephine holes were made about three millimeters back of 

 the fronto-parietal suture. The scalpel was passed back from 

 these to destroy the temporal lobes. The animal had been 



