CEREBRAL FUNCTION IN LEARNING 79 



walking with his left feet near the edge of a table suggested that of 

 Vincent's blind rats after removal of the vibrissae. Training was begun 

 41 days after the operation. The animal was normally active, but at 

 first failed to restrict his reactions to the problem box, as most normal 

 animals do. Nevertheless, he learned with unusual quickness. 

 The brain was preserved 70 days after operation. 



Number of trials required for learning 54 



Per cent of total cortex destroyed 50 



The brain was removed and fixed 91 days after operation. 



Lesion: Plate I, figure 3. Practically all of the left hemisphere was 

 destroyed, leaving only a thin membranous sac containing remnants of 

 the corpus striatum and hippocampus surrounding the thalamus. 



Number 4- Medium sized male. Right hemisphere injured by trans- 

 verse and longitudinal incisions. He developed a slight paresis of the 

 left legs with a possible reduction in the sensitivity of the left face. 

 Training was begun 40 days after operation. The animal learned to 

 go quickly to the platforms in the correct order, but usually merely 

 sniffed at them and then ran to the door. 



Number of trials required for learning 78 



Per cent of total cortex destroyed. 42.4 



The brain was removed and fixed 90 days after the operation. 



Lesion: Plate I, figure 4. The frontal pole of the right hemisphere 

 was completely severed by a section passing just in front of the forceps 

 of the corpus callosum. The dorsal surface of the hemisphere was de- 

 stroyed except for a small area above the corpus striatum and another 

 on the mesial surface of the occipital pole. On the lateral surface a 

 section extended from the lateral ventricle through the posterior mar- 

 gin of the corpus striatum to the surface of the cortex, and the entire 

 temporal and occipital regions caudad to this were degenerated and 

 filled by a large cyst. The hippocampal lobe seemed to be uninjured, 

 although compressed by the cyst. The posterior part of the corpus 

 striatum was destroyed. 



Number 5. Medium sized male. The left hemisphere was injured. 

 He developed a marked right hemiparesis. Training was begun 40 

 days after the operation. His reactions to the problem box were normal. 



Number of trials required for learning 72 



Per cent of the total cortex destroyed 26.6 



