740 A MANUAL OF PHYSIOLOGY 



of its cerebrum has been seen to dart upon a worm, seize 

 it before it had time to sink to the bottom of the aquarium, 

 and swallow it. Even in the pigeon the loss of the hemi- 

 spheres, which at first induces a state of profound and 

 seemingly permanent lethargy, is to a great extent com- 

 pensated for, as time passes on, by the unfolding in the lower 

 centres of capabilities previously dormant or suppressed. 

 A brainless pigeon has been known to come at the whistle 

 of the attendant and follow him through the whole house. 



In the mammal the removal of the whole or the greater 

 part of the cerebral hemispheres at a single operation is 

 uniformly and speedily fatal ; even rabbits or rats, which 

 bear the operation best, survive but a few hours. During 

 those hours they manifest phenomena similar to those ob- 

 served in the bird and the frog. In the dog the entire cortex 

 has been removed piecemeal by successive operations. In 

 this case, of course, the change in the condition of the animal 

 is more gradually produced, and an opportunity is afforded 

 for a certain recovery of function in the intervals between 

 the operations. On the whole, however, as might be expected 

 from its greater intellectual development, recovery is more 

 imperfect in the dog than in the bird, much more imperfect 

 than in the frog. But even in the dog wonderful resources 

 lie hidden in the grey matter of the central neural axis, and 

 are called forth by degrees to replace the lost powers of the 

 cerebral cortex. It is true that a ' brainless ' dog is a less 

 efficient animal than a brainless fish, or even than a brainless 

 frog ; but in favourable cases even in the dog, the movements 

 of walking may still be carried out with tolerable precision 

 in the absence of the cerebral hemispheres. The animal 

 can swallow food pushed well back into the mouth, although 

 it cannot feed itself. Stupid and listless as it is compared 

 with the normal dog, it seems to be by no means devoid 

 of the power of experiencing sensations as the result of 

 impressions from without, nor of carrying on mental opera- 

 tions of a low intellectual grade. Goltz had a dog which 

 lived more than a year and a half practically without its 

 cerebral hemispheres, and another which lived thirteen 

 weeks. He believes that they had lost understanding, 



