430 THE NERVOUS SYSTEM. 



Furthermore, in the experiments on the monkey by Ferrier,* which 

 have given to this subject a great extension, the motor centres were 

 found to occupy a similar region. In this animaj the general form of 

 the hemispheres is so similar to that in man that the principal fissures 

 and convolutions can be recognized without difficulty ; and by stimu- 

 lating various points of the anterior and posterior central convolutions, 

 with others more or less closely adjacent, the same kind of definite 

 movements are produced as in the dog by stimulation of the motor 

 region. 



Lastly, in man, there is now a large body of evidence to the same 

 effect. It consists of numerous cases observed or reported by Charcot,f 

 Ferrier, J Rendu, and Grasset,|| in which there were local epileptiform 

 convulsions on one side coexisting with irritation of the opposite cen- 

 tral convolutions, or hemiplegia caused by their disorganization. Ac- 

 cording to Rendu, local lesions of small extent, when seated in the 

 motor region, produce hemiplegia ; while others of large area, some- 

 times occupying nearly a whole lobe, if outside this region, are not 

 accompanied by paralysis. The hemiplegia in man, resulting from dis- 

 organization of the cortex in the motor region, is complete and perma- 

 nent, and is not associated with any loss of sensibility. 



II. The centres of sensation in the cortex of the brain have not 

 been localized to the same extent nor with the same certainty as the 

 centres of motion. There is reason to believe that the power of per- 

 ception for sensitive impressions in general has its seat in some part 

 of the cerebral cortex, and that it is located in the posterior region 

 of the hemispheres ; since a loss of sensibility on the opposite side of 

 the body, both in the higher animals and in man, is produced by 

 lesions of the posterior part of the internal capsule. According to the 

 experiments of Flourens,<| all distinct perception, both general and 

 special, disappears in the pigeon after removal of both hemispheres ; 

 and after removal of a single hemisphere sight is abolished in the eye 

 of the opposite side. 



The power of visual perception is especially located by Ferrier** in 

 the angular convolution. This observer found that, in the dog, the 

 cat, and the monkey, electrical stimulation of this convolution caused 

 rotation of the eyeballs and sometimes turning of the head toward the 

 opposite side, with contraction of the pupils, as if from a visual sensa- 

 tion ; and in the monkey destructive lesions of the angular convolution 

 produced blindness of the opposite eye, while vision remained in the 



* Functions of the Brain. London, 1876. 



f Lepons sur les Localisations dans les Maladies du Cerveau. Paris, 1878, p. 166. 

 | The Localization of Cerebral Disease. London, 1879, p. 42. 

 I Revue des Sciences Medicales. Paris, 1879, tome xiii., p. 314. 

 || Des Localisations dans les Maladies Ce"re"brales. Paris, 1880, p. 143. 

 fl Kecherches Experimentales sur les Proprietes et les Fonctions du Systeme Ner- 

 veux. Paris, 1842, pp. 31, 123. 

 ** Functions of the Brain. London, 1876, p. 180. 



