314 PROFESSOR MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES. 



Unfortunately I am rather doubtful of it, and in this uncertainty I again beg the 

 reader to follow me in the discussions that I shall be compelled to make upon the 

 different hypotheses that may be imagined by which to interpret the phenomenon of 

 induced contraction. 



I. It is sufficient to have once seen the induced contraction originated by arousing 

 the inducing contraction by any mechanical stimulus, to no longer have any kind of 

 suspicion that the electric current used for exciting the contraction is propagated to 

 the nerve of the galvanoscopic frog*. How must we understand the induced con- 

 traction of the second and third order ? How are we to explain the fact that the in- 

 duced contraction is wanting (although the current may be applied as usual upon 

 the lumbar plexuses of the inducing frog), only because by the section of the nerves in 

 the thigh the inducing contraction is prevented, or at least greatly weakened ? Why 

 is the induced contraction wanting when we apply the same current upon the nerves 

 below the thigh in which there are no inducing contractions ? Why, when we act with 

 a current upon the lumbar plexuses of a frog already weakened so as no longer to 

 have the contractions except at the beginning of the direct current or the cessation 

 of the inverse, why in these cases alone is there. induced contraction? 



It is useless to continue to enumerate the objections that may be made to the in- 

 terpretation of induced contraction by referring to the diffusion of the current exci- 

 ting the inducing contractions, a diffusion that can in no way be physically con- 

 ceived. 



II. It might be suspected that the induced contraction was the result of a mecha- 

 nical stimulus — of the shock of the inducing muscles, which, in their contraction, 

 shake the nerve of the galvanoscopic frog. I have attempted many times (using 

 extremely delicate galvanoscopic frogs) to produce motion in the muscular masses of 

 the thighs in every possible way, and I never could see the galvanoscopic frog contract 

 itself. If the occasion of the phenomenon were this shock, how could we explain 

 the cessation of the induced contraction by the interposition of a very thin sheet of 

 gold leaf or mica between the nerve and the muscle ? 



I have very many times tried to apply the nerve of the galvanoscopic frog upon 

 plates of metal and glass, upon stretched membranes, upon cords of catgut while 

 they were vibrating, and there was never any sign of contraction in the galvano- 

 scopic frog. It is not then the shock of the muscle in contraction against the nerve 

 of the galvanoscopic frog that occasions the induced contraction. 



III. It happens very rarely that the contraction in the galvanoscopic frog is ob- 

 tained when the nerve is being stretched over the thigh of the other frog, and this 

 even when both are perfectly insulated. It is however certain that every time that 

 this happens the occasion does not fail to be discovered. It either consists in 



* Through excess of caution I have many times endeavoured to obtain the induced contraction by exciting 

 the inducing contraction from the laceration of the spinal marrow by means of a fragment of glass ; the induced 

 contraction has taken place as if the inducing contraction had been excited by the current, or by any other 

 stimulus. 



