78 K. S. LASHLEY 



but in all of the others a very large proportion of the hemisphere 

 was destroyed. Brief descriptions of the training and extent of 

 the injuries in each of the animals follow. 



Number 1. Large male. Left hemisphere injured by transverse 

 and longitudinal incisions. Recovery was very rapid without discov- 

 erable sensory or motor disturbance. Training was begun 20 days 

 after the operation. The reactions were prompt from the first and 

 habitual reactions to the door of the problem box appeared on the fifth 

 trial. 



Number of trials required for learning 141 



Per cent of total cortex destroyed 27 



Lesion: Plate I, figure 1. The entire frontal pole of the left hemi- 

 sphere cephalad to the corpus striatum was completely destroyed by 

 a section extending into the olfactory tract. On the dorsal surface 

 the lesion extended caudad to the posterior margin of the hippocampus, 

 involving all the cortex overlying the corpus callosum. The cortex over- 

 lying the corpus striatum and the orbital surface remained intact. 

 Behind this the lesion extended laterad to involve all the cortex over- 

 lying the hippocampus to the level of the posterior commissure. The 

 underlying structures were practically uninjured. 



Number 2. Large male. Left hemisphere injured by tranverse and 

 longitudinal incisions, with an attempt to preserve the corpus striatum. 

 Recovery was rapid without sensory or motor disturbance. Training 

 was begun 20 days after the operation. The behavior of the animal 

 seemed quite normal. 



Number of trials required for learning 132 



Per cent of total cortex destroyed 40.7 



Lesion: Plate I, figure 2. The entire cortex of the left hemisphere, 

 cephalad to the posterior margin of the lobus hippocampus had been 

 separated from the underlying structures and was reduced to a thin 

 membrane. A small area on the occipital pole and the cerebellar sur- 

 face alone remained intact. The olfactory lobe was completely severed. 

 The subcortical nuclei remained uninjured. 



Number 3. Small male. Left hemisphere injured by deep trans- 

 verse and longitudinal incisions. He recovered somewhat slowly and 

 showed a pronounced hemiparesis with rotation to the right in walking. 

 The left vibrissae seemed insensitive and the behavior of the animal in 



