286 NERVOUS FORCE. LECT. XIV. XV. 



nerve. And we have seen that the insulation produced by 

 them was capable of intercepting the propagation of the 

 proper or muscular currents. How can we suppose now, 

 from these facts, that the induced contraction takes its origin 

 from the circumstances which we have before enumerated, 

 even by admitting that they are rendered stronger, or are 

 excited, by the muscular contraction ? 



These circumstances can only arise from a phenomenon 

 of the muscular or the proper current which ought to traverse 

 the nerve of the galvanoscopic frog, even when the latter is 

 surrounded by a layer of an insulating substance, which we 

 have seen cannot be the case. 



4thly, The first idea which presented itself, to explain 

 induced contraction, was to admit that there was a develop- 

 ment of electricity accompanying muscular contraction. 

 There is a disengagement of heat during the contraction ; 

 there may be even cases where light might accompany it, 

 according to the observations of Quatrefages, observations 

 which deserve, on account of their great importance, to be 

 repeated in order to study more fully all their peculiarities. 



Hence, therefore, a certain degree of analogy would 

 authorize us to regard as probable the production of electri- 

 city during the muscular contraction. Moreover, the few 

 experiments which I made when I discovered induced con- 

 traction, would be equally explained, and in as satisfactory 

 a manner, by this hypothesis. An insulating body, such as 

 a leaf of mica, or glazed paper, prevents, by its interposi- 

 tion, the induced contraction from taking place. The like 

 result occurs when a leaf of gold, discharging perfectly the 

 electricity which we presume is developed during contrac- 

 tion, prevents the nerve from being traversed by it. 



Notwithstanding these first suppositions, which we made 

 in the hope of being able to furnish a simple explanation of 

 induced contraction, and at the same time a demonstration 



