190 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



appropriate feeding and so long as it is well fed retains its stupid 

 and impassive appearance. If allowed to starve for a while it 

 becomes restless from the effects of hunger, may walk to and fro, 

 and peck aimlessly at the ground. If surrounded by grain it may 

 peck at the separate grains, but never actually seizes one in its 

 beak and swallows it. The striking defect in these animals is the 

 loss of those responses that depend upon memory of past or in- 

 herited experiences. Its motor reactions are all of a simple kind. 

 If placed upon a hot plate it will, for a time, lift first one foot, then 

 the other, and finally squat, but never flies away. When dosing 

 a loud noise awakens it, but it exhibits no signs of fear, and 

 quickly relapses into somnolence when the auditory stimulus ceases. 

 The one positive conclusion that we may draw from the behavior 

 of these animals is that in them the cerebrum is the organ in 

 which the memory associations are mediated, and that when it 

 is removed the actions of the animal become much more direct 

 and predictable, since the stimulus aw\akens no associations with 

 past experiences. The complete removal of the cerebrum in mam- 

 mals is attended with more difficulty. When taken out at once 

 by a single operation, the animal survives but a short time and 

 the permanent effects of the operation cannot be detected. Goltz,* 

 however, has succeeded, in dogs, in removing by a peculiar opera- 

 tion all of the cerebral cortex. The operation was performed in 

 several successive stages with an interval of several months between. 

 In the most successful experiment the animal was kept alive for 

 a year and a half and the postmortem examination showed that 

 all of the cortex had been removed except a small portion of the 

 tip of the temporal lobe, and this latter, since its connection with 

 the other parts of the brain had been destroyed, was, of course, 

 functionless. In addition, a large part of the corpora striata and 

 the thalami and a small portion of the midbrain had been re- 

 moved. The behavior of this animal was studied carefully. After 

 the immediate effects of the operation — paralysis, etc. — had disap- 

 peared the animal moved easily; in fact, showed a tendency to keep 

 moving continually. There was no permanent paralysis of the so- 

 called voluntary movements. He answered to sensory stimuli of 

 various kinds, but not in an intelligent way. If, for instance, a 

 painful stimulus was applied to the skin, he would growl or bark, 

 and turn his head toward the place stimulated; but did not attempt 

 to bite. No caressing could arouse signs of pleasure, and no 

 threatening signs of fear or anger. Like the pigeon, the most con- 

 spicuous defect in the animal was a lack of intellic^ont response, — ■ 

 that is, the responses to sensory stimuli were simple, and evidently 



* Goltz, "Archiv f . die gesammte Physiologie," 51, 570, 1892. 



