ON INDUCED CONTRACTIONS. 315 



the inside of the muscle being uncovered in some points, or because the nerve of the 

 galvanoscopic frog remains united to some piece of muscle, that folding back again 

 touches the nerve when this is extended over the thigh. It has also appeared to me 

 that sometimes these contractions occur when the tendinous extremities and the sur- 

 face of the muscle and of the thigh touch two points of the nerve of the galvanoscopic 

 frog. So let us say that the induced contraction takes place constantly in all cases 

 in which, by the care taken, the above-mentioned circumstances that may awake the 

 contraction of the galvanoscopic frog are verified. We know too that having cut with 

 scissors the muscular superficies of the thighs, and rendered them thus quite uniform, 

 the induced contraction continues, when the nerve of the galvanoscopic frog is ap- 

 plied upon the new internal surface of the muscle. This induced contraction sub- 

 sists even through the skin of the frog, and on interposing insulating liquid layers be- 

 tween the nerve and the muscle. We have seen that the insulating power of those 

 layers was such as not to permit the circulation of the proper and muscular currents. 

 How then can it be supposed that the induced contraction should take its origin 

 from the above stated circumstances, even admitting that they may be rendered more 

 active, or that they may be excited by the muscular contraction ? These circumstances 

 reduce themselves to the phenomenon of a muscular current or of a proper current, 

 which ought to traverse the nerve of the galvanoscopic frog, while that nerve would 

 be enveloped by a stratum of an insulating substance, which we have seen cannot be. 



IV. The first idea conceived by which to interpret the induced contraction, was 

 that of an evolution of electricity which might accompany the muscular contraction. 

 There is evolution of heat in the act of contraction ; and, according to the important 

 observation of Quatrefage, which there is much necessity for repeating, in order to 

 exactly establish its details, there would appear to be development of light in certain 

 cases of muscular contraction ; so that analogy might lead us to infer the probability 

 of the production of electricity by the muscular current : besides, the few experi- 

 ments that I made when I discovered the induced contraction might very well be in- 

 terpreted on this hypothesis. An insulating body, as a lamina of mica or varnished 

 paper, when interposed, impeded the induced contraction : and it could not be other- 

 wise. The same thing occurred even when a lamina of gold perfectly discharging 

 the electricity, that it is supposed is produced by the contraction, prevented the 

 nerve from being traversed by it. 



In spite of these first steps, which were flattering me into giving a very simple ex- 

 planation of the induced contraction and were leading me at the same time to prove 

 an important phenomenon in the muscular contraction, I am now constrained to 

 entirely abandon this idea because it is contradicted by experiment. 



In the beginning of tliis memoir, I referred at all possible length to the many ex- 

 periments made by which to examine if there is any augmentation of the muscular 

 current, or of the proper one in the act of contraction. All my efforts have been 

 useless, and I have been obliged to conclude that experience does not prove that the 

 signs of the muscular or proper currents increase in the act of muscular contraction. 



MDCCCXLV. 2 T 



