422 THE BBAIIST. 



hearing, or of ordinary sensibility. All these functions remain, as 

 well as that of voluntary motion. If a pistol be discharged behind 

 the back of the animal, he at once opens his eyes, moves his head 

 half round, and gives evident signs of having heard the report ; but 

 he immediately becomes quiet again, and pays no farther attention 

 to it. Sight is also retained, since the bird will sometimes fix its 

 eye on a particular object, and watch it for several seconds together. 

 Longet has even found that by moving a lighted candle before the 

 animal's eyes in a dark place, the head of the bird will often follow 

 the movements of the candle from side to side or in a circle, showing 

 that the impression of light is actually perceived by the sensorium. 

 Ordinary sensation also remains, after removal of the hemispheres, 

 together with voluntary motion. If the foot be pinched with a 

 pair of forceps, the bird becomes partially aroused, moves uneasily 

 once or twice from side to side, and is evidently annoyed at the 

 irritation. 



The animal is still capable, therefore, after removal of the hemi- 

 spheres, of receiving sensations from external objects. But these 

 sensations appear to make upon him no lasting impression. He is 

 incapable of connecting with his perceptions any distinct succession 

 of ideas. He hears, for example, the report of a pistol, but he is not 

 alarmed by it ; for the sound, though distinctly enough perceived, 

 does not suggest any idea of danger or injury. There is accord- 

 ingly no power of forming mental associations, nor of perceiving 

 the relation between external objects. The memory, more particu- 

 larly, is altogether destroyed, and the recollection of sensation is 

 not retained from one moment to another. The limbs and muscles 

 are still under the control of the will ; but the will itself is inactive, 

 because apparently it lacks its usual mental stimulus and direction. 

 The powers which have been lost, therefore, by destruction of the 

 cerebral hemispheres, are altogether of a mental or intellectual 

 character ; that is, the power of comparing with each other different 

 ideas, and of perceiving the proper relation between them. 



The same result is well known to follow, in the human subject, 

 from injury or disease of these parts. A disturbance of the mental 

 powers has long been recognized as the ordinary consequence of 

 lesions of the brain. In cases of impending apoplexy, for example, 

 or of softening of the cerebral substance, among the earliest and 

 most constant phenomena is a loss or impairment of the memory. 

 The patient forgets the names of particular objects or of particular 

 persons ; or he is unable to calculate numbers with his usual facility. 



