94 8 THE CENTRAL NERVOUS SYSTEM 



perfect rest, and when stimulated, moves for a considerable distance. 

 Alter a time two months or more it is true the brainless frog, 

 if it be kept alive, as may be done by careful attention, -will recover 

 a certain portion of the powers which it has lost by removal of the 

 cerebral hemispheres ; and, indeed, the longer it li ves, the nearer it 

 approximates to the condition of a normal frog. A brainless frog 

 has been seen to catch flies and to bury itself as winter drew on. 

 A fish even three days after the destruction 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 hemispheres, which at first induces a state of profound 

 and seemingly permanent lethargy, is to a great extent compensated 

 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 observed 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, pre- 

 cision 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, or of carrying 

 on mental operations 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, reflection, and 

 memory, but not sensation, special or general, nor emotions and 

 voluntary power. Their condition may be best described as one of 

 general imbecility. Hunger and thirst are present. They experi- 



