THE HEMISPHERES. 483 



short time after the operation shake the head briskly in consequence of 

 a fly having alighted on the wound. Hearing and sight also remain. 

 The discharge of a pistol behind the back of the pigeon will often cause 

 him to open his eyes and turn his head partially round, giving evident 

 signs of having heard the report ; though he immediately becomes quiet 

 again and pays it no further attention. In a rat which had been sub- 

 jected to this operation by Yulpian, a sharp hissing sound made by the 

 lips produced a sudden start and movement of the whole body. The 

 same observer found that in a pigeon, after the animal had been roused 



Fig. 160. 



PIGEON, AFTER REMOVAL OF THE CEREBRAL HEMISPHERES. 



by pinching the foot, the sudden approach of a hand toward the eye 

 caused a winking movement with partial turning of the head. Some- 

 times such a pigeon will fix his eye on a particular object, and watch it 

 for several seconds together. Longet found that by moving a lighted 

 candle before the animal's eyes in a dark place, the head of the bird would 

 often follow the movements of the candle, showing that the impression 

 of light was perceived. 



The animal is still capable, therefore, after removal of the hemispheres, 

 of receiving sensations from external objects. But these sensations 

 make upon him no lasting impression. He is incapable of connecting 

 with his perceptions any distinct succession of ideas. If he hears the 

 report of a pistol, he is not alarmed by it ; for the sound, though dis- 

 tinctly enough perceived, does not suggest any idea of danger or injury. 

 There is accordingly no power of perceiving the relation between ex- 

 ternal objects. The memory, particularly, is destroyed, and the recol- 

 lection of sensations is not retained from one moment to another. The 

 muscles are still under the control of the will ; but the will itself is 

 inactive, because it lacks its usual stimulus and direction. The powers 

 which have been lost, therefore, are those of a mental character ; that is, 

 the power of comparing different sensations or ideas, of perceiving the 



