30 Mr H. F. Baxter on the Effects of Acid and Alkalies 



following. If a current of electricity be made to traverse a 

 portion of a nerve connected with the muscles, a difference 

 will be observed in the effects, as manifested by the muscu- 

 lar contractions, when the current is suspended. The 

 muscles of the limb w^iose nerve has been traversed by an 

 inve7^se current will contract tetanically; whilst the muscles, 

 if the current be direct^ will contract but once — the tetanic 

 contractions being very rarely jjroduced. These effects vary 

 according to the strength of the current and the time of its 

 passage. Matteucci,* in his papers on the " Physiological 

 Action of the Electric Current,'' came to the conclusion that 

 the passage of the electric current through a mixed nerve 

 produces a variation in the excitability of the nerve, dif- 

 fering essentially in degree, according to the direction of 

 the current through the nerve. This excitability being- 

 weakened and destroyed, and that more or less rapidly, ac- 

 cording to the intensity of the current, w^hen it circulates 

 through the nerve from the centre to the periphery (direct 

 current). The excitability, on the contrary, being pre- 

 served and increased by the passage of the same current in 

 a contrary direction, that is to say, from the periphery 

 towards the centre (inverse current). But in a subsequent 

 paper t on the " Secondary Electro-Motor Power of Nerves," 

 he refers the effects to a secondary electro-motor power, and 

 says, " the secondary current, the existence of which is 

 demonstrated by the galvanometer, and which is direct for 

 the nerve that has been traversed by the inverse current, 

 and which is also demonstrated by the contractions of the 

 galvanoscopic frog [placed upon the nerve], explains, accord- 

 ing to the known laws of electro-physiology, the effects 

 produced by it on the opening of the circuit." 



" If any part of a nerve," says Du Bois Keymond,J " be 

 submitted to the action of a permanent current, the nerve, 

 in its whole extent, suddenly undergoes a material change in 

 its internal constitution, which disappears on breaking the 

 circuit as suddenly as it came on. This change, w^hich is 

 called the Electro-tonic state, is evidenced by a new electro- 

 motive pow^r, which every point of the whole length of the 



* Phil. Trans., 1846, 1847, t Ibid., 1861. 



X On Animal Electricity, Edited by H. Eence Jones, M.D., p 213. 



