Chap, iv.] PEOPEKTIES OF NERVOUS FIBRES. 397 



but slowly. It produces no apparent effect upon planaries, 

 asterias, and fresh water polypi. ^ In short it is specially 

 upon the white fibres of animal Hfe that its action is 

 prompt and sure. The gelatiniform fibres resist it better. 

 In man even, the sympathetic nerve is difficult to touch, 

 and those organs which, like the heart, receive simultane- 

 ously white and grey fibres, are the last to be smitten. As 

 the chief difference between the white fibres and those named 

 after Kemak seems to consist in the presence of a manica of 

 myeline in the first, which is absent in the others, we should be 

 tempted to believe that the curare acts specially upon this 

 medullary substance ; but in this case, as in so many biological 

 phenomena, the conditions are too complex to lend themselves 

 readily to such simple explanations. In fact, it is from the 

 periphery to the centre that curard effects the toxication of the 

 nerve; the peripheric extremities of the nerve are first and 

 perhaps solely struck, since a motory nerve, separated from the 

 marrow by section, is still poisoned by the curarised blood which 

 bathes its extremities.^ Now exactly by penetrating into the 

 muscles, the nervous motory fibres divest themselves of their 

 oUy envelopment, and assume in some degree the aspect of the 

 fibres of Remak. It has been supposed that curar^ did not 

 provoke profound lesions in the nervous fibre. In fact, the 

 living nervous fibre, like the muscular fibre and certain vegetal 

 fibres, produces an electric current, going from the surface to its 

 centre of section; now the nervous fibre, physiologically de- 

 stroyed by curare, is still the seat of the ordinary electric 

 phenomena ; consequently, life has never quitted it, and the 

 nutritive exchange is always taking place. Here then we must 

 admit either delicate and invisible molecular perturbations, or 

 perhaps a simple depression of the nutritive energy, sufficient to 

 abolish the special function, but not yet reaching the funda- 

 mental basis of life. 



' Vulpian, loe. at., p. 201. 



' CL Bernard, Rapp(yrt sm-les Progris de la Physiologie, p. 19. 



