FUNCTIONS OF THE BRAIN 9^ 



The animal, as soon as the effects of the anaesthetic and the shock 

 of the operation have passed away, draws up its legs, erects its head, 

 and assumes the characteristic position of the normal frog at rest. 

 So close maybe the resemblance, that if all external signs of the opera- 

 tion have been concealed, it may not be possible for a casual ob- 

 server to tell merely by inspection which is the intact and which the 

 ' brainless ' frog. The latter will jump if it be touched or otherwise 

 stimulated. It will croak if its flanks be stroked or gently squeezed 

 together. It will swim if thrown into water. If placed on its back, 

 it will promptly recover its normal position. But it will do all 

 these things as a machine would do them, without purpose, without 

 regard to its environment, with a kind of ' fatal ' regularity. 

 Every time it is stimulated it will jump, every time its flanks are 

 squeezed it will croak, and, in the absence of all stimulation, it will 

 sit still till it withers to a mummy, even by the side of the water 

 that might for a while preserve it. 



A Necturus, without its cerebral hemispheres, will, like the frog, 

 refuse to lie on its back. On stimulation it moves its feet or tail, 

 or its whole body; but if not interfered with, it lies for an indefinite 

 time in the same position. Its gills are seen to execute rhythmic 

 movements, which never stop, and rarely slacken, except for an 

 instant, when some part of the skin, particularly in the region of 

 the head, is mechanically or electrically stimulated. The normal 

 Necturus, on the other hand, lies for long periods with its gills at 

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

 After 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 lives, 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 



