434 THE NERVOUS SYSTEM. 



finally with the peripheral organs. If these tracts be injured in any 

 part of their course, hemiplegia, hemianeesthesia, or both, may follow 

 as a consequence. 



The locality of lesions producing hemiplegia is in the anterior por- 

 tion of the internal capsule. In the experiments on dogs by Carville 

 and Duret,* section of the internal capsule in this region, between the 

 caudate nucleus and the lenticular nucleus, was constantly followed by 

 hemiplegia of the opposite side of the body. In man, the results of 

 pathological observation are to the same effect. According to Charcot,f 

 although destructive lesions, limited to the gray substance of the corpus 

 striatum or optic thalamus, may produce symptoms of hemiplegia, the 

 paralysis in these instances is usually incomplete and transitory : and 

 is often to be referred, in cases of hemorrhagic effusion, to temporary 

 compression of the internal capsule. On the other hand, lesions con- 

 fined to the internal capsule, in its anterior two-thirds, produce an oppo- 

 site hemiplegia which is strongly marked and persistent, and usually 

 unaccompanied by any loss of sensibility. The destruction of conti- 

 nuity in the fibres of the internal capsule from such injuries is final, and 

 the resulting paralysis is consequently permanent. 



The production of hemiansesthesia from lesions of the internal cap- 

 sule is limited, in an analogous way, to its posterior portion. The 

 region of cortical substance devoted to the perception of tactile sensa- 

 tions has not been determined to the general satisfaction of physi- 

 ologists. But there is reason to believe that it is seated somewhere 

 in the posterior portion of the hemisphere ; and there is no question 

 that the communicating tracts of centripetal fibres, subservient to this 

 function, are in the hinder part of the internal capsule. The extreme 

 posterior border of this capsule is formed by the direct sensitive fibres 

 from the outer part of the crura cerebri already mentioned (page 422) 

 as described by Gratiolet. In the experiments of YeyssiereJ on dogs, 

 it was shown that for the production of persistent hemiansesthesia 

 from cerebral Jesions, it was indispensable that the injury involve 

 the fibres of the internal capsule. 



According to the researches of Carville and Duret, already quoted, 

 it appears that while a destructive injury in the anterior portion of the 

 internal capsule causes hemiplegia without hemianaesthesia, a lesion of 

 its posterior portion is followed by hemianaBsthesia without hemiplegia. 

 In each case the morbid effects are produced on the opposite side of 

 the body. The same rule holds good in man. According to Charcot, 

 the question whether a lesion in the neighborhood of the cerebral 

 ganglia shall produce loss of motion or loss of sensibility depends on 

 which part of the internal capsule it involves. If seated in the anterior 

 two-thirds it produces hemiplegia ; if in the posterior third, it is a hemi- 



* Archives de Physiologic. Paris, 1875, 2me serie, tome ii., p. 352. 

 f Lecons sur les Localisations dans les Maladies du Cerveau. Paris, 1878 pp. 96 

 98, 99, 100. 



t H^mianaesthesie de Cause Cer^brale. Paris, 1874, p. 73. 



