100 



K. S. LASHLEY 



This result is due, however, solely to the position of animal num- 

 ber 1, which showed average destruction and slow learning. If 

 he is included with the lower group the relations are reversed to 

 10 per cent in favor of the group with greater destruction. 



We may conclude, therefore, that the differences here are not 

 significant. Paresis gives the animal a slight advantage in learn- 

 ing the double-platform box, but aside from this the extent of 

 injury does not affect the rate of learning. Amounts of injury 

 from 14 to 50 per cent of the entire cerebral cortex do not result 

 in any correlated alteration in the animals' learning ability. 



TABLE 6 



The relation of the quantity of cerebral cortex destroyed to the rate of learning in ani- 

 mals trained on the double-platform box. On the left are the animals with less 

 than the average destruction, on the right those with more than the average 



None of this evidence really settles the question of the signifi- 

 cance of the apparent superiority of the operated animals over 

 normals. The data on paretic animals and on the relation of 

 the extent of the injury to the rate of learning do suggest, how- 

 ever, that the reduction in vigor is the chief cause of the differ- 

 ence and also give some indication of the actual extent to which 

 such reduction has influenced the results. The existence of an 

 observable paretic condition is able to produce a superiority of 

 28 per cent over the learning rate of non-paretic operated ani- 

 mals (page 92). The difference in vigor between the non-paretic 



