292 NERVOUS SYSTEM. 



responding side of the body remains as one of the first ex- 

 perimental arguments in favor of the crossed action. 



Experiments upon living animals as well as pathological 

 facts show that, after section or injury confined to one lateral 

 half of the cord, the general sensibility upon the correspond- 

 ing side of the body is very much exaggerated, producing a 

 condition of well-marked hypersesthesia. This remarkable 

 fact was distinctly noted by Fodera, in 1822: "Having di- 

 vided, in a Guinea-pig, the right superior column of the cord 

 in the middle of the dorsal region, the sensibility of the flank 

 and of the posterior extremity of the same side was more 

 exquisite than in every other part of the body, and it seemed 

 that the movements of the same extremity possessed greater 

 energy." ] This observation was confirmed, and the experi- 

 ments were very much extended, by Brown-Sequard. 2 Cases 

 presenting the same phenomena have also been observed in 

 the human subject, when one side of the cord has been in- 

 vaded by disease. 3 



Physiologists are at a loss to explain the hypersesthesia 

 which follows section of the sensory conductors of the cord, 

 but the fact nevertheless remains. The exaggeration of sen- 

 sibility is not due to section of certain fibres, which might 

 be supposed to increase the impressibility of the remaining 

 fibres, for, as was shown by Yulpian, it is sufficient to prick 

 with a pin one of the lateral halves of the cord to observe 

 these remarkable phenomena. 4 "With these few words, we 

 will leave the subject of hypersesthesia from injury to the 

 cord, and pass to the crossed action of its sensory con- 

 ductors. 5 



1 FODERA, Journal de physiologic, Paris, 1823, tome iii., p. 200. 



2 BROWN-SEQUARD, Experimental Researches applied to Physiology and Pathol- 

 ogy, New York, 1853, p. 64, el al 



3 BROWN-SEQUARD, Recherches sur la transmission des impressions de tad, de 

 chatouillement, de douleur, de temperature et de contraction (sens musculaire) dans 

 let moette epinere. Journal de la physiologie, Paris, 1863, tome vi., p. 645. 



4 VULPIAN, Systeme nerveux, Paris, 1866, p. 388. 



5 For further experiments showing the effects of transverse section of the 



