126 HUMAN PHYSIOLOGY 



swerve toward a perch. Having alighted it sinks into 

 its customary moping attitude. Loud sounds cause 

 it to stir, but sluggishly. It will not find food for itself 

 though it may be within easy reach. It does not re- 

 spond to the presence of its own kind nor is it disturbed 

 by the approach of its natural enemies. Associative 

 memory is gone and little or no power to form fresh 

 associations is left. 



The removal of the cerebrum from a mammal was 

 long supposed to be impossible. It was triumphantly 

 accomplished about twenty-five years ago and the feat 

 has been repeated many times. In the first successful 

 decerebration of a dog .the brain substance was cau- 

 tiously washed from the cavity of the skull, the process 

 being completed in three stages with long intervals to 

 permit recovery from the shock. The dog rallied well 

 and was kept in fair condition for more than a year, 

 though toward the last its strength was failing. It 

 was finally killed and the autopsy showed that cerebrum 

 had been wholly obliterated. 



This dog gave the same general impression which one 

 derives from watching a decerebrate pigeon. The 

 animal was mechanically competent but idiotic. It 

 roved about the laboratory, making detours around 

 objects in its path and taking the same pains to avoid 

 patches of sunlight on the floor. It chewed and swal- 

 lowed food which was brought to its mouth but did 

 not seek it. It would snap at the hand of anyone who 

 pinched it but only during the irritation; it did not con- 

 ceive of such a one as an enemy, and harbored no preju- 

 dice against him. It was questionable whether k ever 

 learned anything by experience after the operations. 



The human cerebrum is very large in proportion to 

 the rest of the nervous system and to the total mass 

 of the body. This coincides with the evident fact that 

 man has less inherited power of coordinated action than 

 most of the lower animals and far more capacity to 

 develop reactions based on memory. We do not make 

 deliberate experiments upon the human brain, but nature 



