FUNCTIONS OF THE BRAIN 947 



and rested on the ground, With most persons the swinging foot first 

 strikes the ground by the heel; then the sole comes down, the heel 

 rises, the leg is extended, and, with a parting push from the toe, the 

 leg again swings free. By this manoeuvre the body is raised vertically, 

 tilted to the opposite side, and also pushed in advance. 



The forward swing of the leg is only slightly, if at all, due to mus- 

 cular action; it is more like the oscillation of a pendulum displaced 

 behind its position of equilibrium, and swinging through that position, 

 and in front of it, under the influence of gravity. For this reason the 

 natural pace of a tall man is longer and slower than that of a short 

 man; but it may be modified by voluntary effort, as when a rank of 

 soldiers of different height keeps step. The lateral swing of the body 

 is illustrated by the everyday experience that two persons knock 

 against each other when they try to walk close together without 

 keeping step. In step both swing their bodies to the same side at 

 the same moment, and there is no jarring. Even in the fastest walk- 

 ing on level ground there is a short time during which both feet touch 

 the ground together, the one leg not beginning its swing until the 

 other foot has begun to be set down. In running, on the other hand, 

 there is an interval during which the body is completely in the air, 

 while in walking uphill or in carrying a load the one foot is not raised 

 until the other has been firmly planted. 



Functions of the Cerebral Cortex. When an animal, like a frog, 

 is deprived of its cerebral hemispheres, the power of automatic 

 voluntary movement appears to be definitively and entirely lost. 

 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 



