274 NERVOUS SYSTEM. 



deep portions. The facts upon which this assertion was 

 based were, that direct stimulation of these portions of the 

 cord in living animals, whether by mechanical means or by 

 feeble galvanic shocks, produced no contraction of muscles 

 and no pain. Upon irritating the posterior columns, either 

 by mechanical or galvanic stimulus, Chauveau noted pain 

 and reflex movements when the irritation was applied to the 

 surface, but the results were negative when the deep por- 

 tions of the columns were operated upon. The surface of 

 the posterior columns seemed to possess the same general 

 properties as the posterior roots of the nerves, especially 

 near the roots, where the sensibility was most marked, 

 gradually diminishing in intensity toward the median line ; 

 but the deep portions of the cord were everywhere found 

 completely insensible and inexcitable. 1 



The experiments and conclusions of Chauveau have a 

 most important bearing upon the physiology of the cord, 

 and are opposed to the views of the majority of physiologi- 

 cal writers, though they have been admitted by some experi- 

 menters. We shall discuss first the experiments upon the 

 antero-lateral columns, which are most remarkable in their 

 negative results. In this we shall use the term excitability 

 as signifying the property of the cord which enables it to 

 conduct a stimulus applied directly to it to certain muscles, 

 producing convulsive movements confined to these muscles, 

 and not of a reflex character. We shall apply the term 

 sensibility to the property by virtue of which an irritation 

 directly applied is conveyed to the brain and produces a 

 painful impression. 



The experiments of Chauveau and some others upon the 

 antero-lateral columns are simply negative ; but their results 

 are directly opposed to those of numerous experimenters, 

 who have produced local and restricted convulsive move- 

 ments by direct irritation of both the superficial and the 



1 CHAUVEAU, De TexcitaUlite de la moelle epinere. Journal de la physiologic, 

 Paris, 1861, tome iv., p. 369. 



