310 THE BIOLOGY OF THE FROG CHAP. 



spheres were carefully removed without injuring the thalami, 

 and the animal kept some months after the operation, spon- 

 taneity of action is by no means lost ; the animals move 

 about from land to water, bury themselves in the mud on the 

 approach of winter, and snap at flies which move within their 

 reach. Their conduct, in fact, resembles very closely that 

 of normal frogs ; and in just what respect it differs Schrader 

 does not make clear. After loss of the cerebral hemispheres 

 all fear, according to Kato, disappears, and the frog no 

 longer croaks spontaneously, but how long after the opera- 

 tion these results were observed is not stated. Since so 

 many of the functions supposed to have their seat in the 

 cerebral hemispheres are shown to be performed by other 

 parts of the brain, it is not definitely established just what 

 roles these organs really play. In higher animals they are 

 the seat of intelligence and voluntary control ; and it is not 

 improbable that whatever intelligence the frog may possess 

 may have a similar local habitation. But this conclusion, 

 probable as it may be, cannot be regarded as established by 

 experiment. 



Removal of one cerebral hemisphere is not followed by 

 so severe shock effects as the removal of the entire cere- 

 brum. The frog thus operated upon is, according to Kato, 

 more active, it springs more readily, and manifests fear upon 

 seeing the approach of large objects. It tends at first to 

 avoid obstacles placed in its path by turning away from 

 the operated side, but in four days after the operation its 

 behavior, according to Loeser, becomes entirely normal. 



If the parietal region of the cerebral hemispheres be stim- 

 ulated by a very weak current of electricity, movements of 

 the limbs are brought about on the opposite side of the 

 body, and usually also, although to a less extent, on the same 

 side, whereas stimulation of other parts of the cerebral 



