CEREBRAL FUNCTION IN THE RAT 



123 



the turn at the end of the central alley by holding to the end 

 of the partition with both left feet and pushing his body around 

 with the right. 



He learned to turn to the right for food after forty trials. 

 The food was then placed in the left alley. The previous habit 

 of turning to the right, reinforced by his motor difficulty in 

 turning to the left made the new habit very difficult for him to 

 acquire and eighty trials were required before he made ten in 

 succession without error. The records of time and errors are 

 given in table 4. 



TABLE 4 

 Rate of learning for rat described in experiment 88 



He was killed 40 days after the operation. A small abscess 

 filled with pus was found over the cranial opening but did not 

 extend into the cortical tissues. There was a deep pit in the 

 cortex, completely exposing the lateral and third ventricles. 

 Microscopic examination showed a complete destruction of the 

 convexity of the cortex including the whole of the corpus callo- 

 sum to the knee (plates I and II, fig. 38). The lesion extends 

 from just behind the corpus callosum diagonally forward to the 

 base of the olfactory lobes, separating the entire frontal pole on 

 either side. The longitudinal incisions extending down over 

 the temporal and orbital surfaces of the cortex to the level of the 

 ventricles with degeneration of neighboring areas. The right 

 corpus striatum is degenerated and infiltrated by large blood 



