272 STUDIES IN PHYSIOLOGY 



normal, and in addition to the reflexes already shown by 

 the lower centers, he croaks regularly whenever he is 

 pinched under the arms." 



Effect of removing the Cerebral Hemispheres. " A frog which 

 has lost his cerebral hemispheres alone is by an unpracticed ob 

 server indistinguishable from a normal animal. Not only is 

 he capable, on proper instigation, of all the acts already 

 mentioned, but he guides himself by sight, so that if an 

 obstacle be set up between himself and the light, and he be 

 forced to move forward, he either jumps over it or swerves 

 to one side. . . . He is, in short, so similar in every re- 

 spect to a normal frog that it would take a person very 

 familiar with these animals to suspect anything wrong or 

 wanting with him ; but even then such a person would soon 

 remark the almost entire absence of spontaneous motion 

 that is, motion unprovoked by any present incitation of 

 sense. The continued motions of swimming, performed 

 by the creature in the water, seem to be the fatal result of 

 the contact of that fluid with the skin. They cease when a 

 stick, for example, touches his hand. ... He manifests 

 no hunger, and will suffer a fly to crawl over his nose 

 unsnapped at. Fear, too, seems to have deserted him." 



Functions of the Cerebral Hemispheres. " But now if to 

 the lower centers we add the cerebral hemispheres, or if, 

 in other words, we make an intact animal the subject 

 of our observations, all this is changed. . . . Our frog 

 now goes through long and complex acts of locomotion 

 spontaneously, or as if moved by what, in ourselves, we 

 would call an idea. His reactions to outward stimuli vary 

 their form too. Instead of making simple defensive move- 

 ments with his* hind legs, like a headless frog if touched ; 

 or of giving one or two leaps and then sitting still like a 

 hemisphereless one, he makes persistent and varied efforts 

 of escape, as if, not the mere contact of the physiologist's 

 hand, but the notion of danger suggested by it were now 

 his spur. Led by the feeling of hunger, too, he goes in 



