180 PHYSIOLOGY OP CENTRAL NERVOUS SYSTEM. 



it swims to a solid support and crawls out like a normal animal. 

 It jumps when stimulated and is careful to avoid obstacles placed 

 in its way, showing that its visual reflexes are not impaired. It 

 is said, however, that the more complicated reactions that depend 

 upon the memory of past experiences or the instincts are absent or 

 imperfect. This latter peculiarity is manifested most impressively 

 in birds (pigeons) after removal of a part or all of the cerebrum. As 

 a result of such an operation, the nervous, active animal is changed 

 at once to a stupid, lethargic creature which reacts only when 

 stimulated. It sits in a drowsy attitude, with its head drawn in 

 to the shoulders, its eyes closed, and its feathers slightly erected; 

 occasionally it will open its eyes, stretch the neck, gape, preen 

 its feathers perhaps, and then sink back into its somnolent attitude. 

 The animal in this condition maintains its equilibrium perfectly, 

 flies well if thrown into the air and perches comfortably upon a 

 narrow support. It may be kept alive apparently indefinitely by 

 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 behavibr 

 of these animals is that in them the cerebrum is the place in which 

 the memory records are stored, and that when it is removed the 

 actions of the animal when stimulated become much more direct 

 and predictable, since the stimulus awakens 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 operation 

 all of the cerebral cortex. The operation was performed in sev- 

 eral 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 

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



