CEREBRAL LOCALIZATION. 605 



ence and topography of a certain number of centers which Ferrier has 

 studied with great care. 



Take, for example, the visual center : its stimulation caused disor- 

 dered reflex actions, indicating unpleasant visual perceptions. This 

 alone is insufficient proof ; but we can control the region in question 

 by ablation, which brings on unilateral or bilateral blindness, accord- 

 ing as we operate on one or both of the visual centers. Stimulation of 

 the auditive centers, in the same part of the brain, provokes move- 

 ments of the ears, eyes, and head, showing astonishment or terror, just 

 like those caused by a violent and unexpected noise. Ablation causes 

 deafness ; the animal remains indifferent to all sounds. Excite the 

 centers of touch, and the signs indicate disagreeable or painful tactile 

 impressions. Ablation brings on complete anaesthesia of the same 

 parts ; you may prick, cut, and bruise the animal, and he remains 

 insensible. 



Some experiments seemed to indicate the existence of centers of 

 taste and odor, but it is difficult to trace their limits. They are inter- 

 mingled like the gustative and olfactive sensations. Electricity causes 

 movements indicating unpleasant tastes and odors, and extirpation of 

 the parts ends these sensations. The animal will respire odors, or taste 

 savors that in the normal state would make him fly about the labora- 

 tory, and it all passes unperceived. Still more hypothetical are the 

 centers of the organic needs of hunger and thirst, and more yet 

 those of sex, but Ferrier's arguments are strong in favor of their 

 existence. 



The presence of a third, or intellectual region, is proved, as far as 

 it can be, by experiments on the lower animals. It is difficult to un- 

 derstand the mental action of a dog, Indian pig, or even of a monkey. 

 Ferrier observed numerous facts tending to establish the intellectual 

 function of the anterior region of the brain. Electricity could hardly 

 be employed in these researches ; but ablations, when performed with 

 caution, brought on notable changes in the habits of animals. The 

 monkeys chosen by Ferrier were remarkable for their vivacity and 

 intelligence, prying about right and left, and observing everything. 

 After the operation they became stupid and apathetic. But these in- 

 dications are not convincing. The clinic alone can decide whether 

 physiology sustains the doctrine of cerebral localization. 



We know in what the clinical method consists. Applied most 

 often to man, it amounts to this : to observe the symptoms of cerebral 

 disease, and at the autopsy to connect the lesions, discovered by the 

 naked eye or the microscope, with the symptoms, as cause and effect. 

 It is true that in cerebral pathology there is great difficulty in separat- 

 ing the essential from the accidental, and distinguishing cause and 

 effect among a plurality of causes. Besides, it frequently happens in 

 cases of cerebral disease that at the autopsy no appreciable lesions can 

 be found. The question is still further complicated by the solidarity 



