LECT. XIV. XV. INDUCED CONTRACTIONS. 287 



of the existence of a very important fact respecting muscu- 

 lar contraction, we are now compelled to abandon entirely 

 this view, since it is disproved by experiment. 



At the commencement of this lecture, I related to you 

 many experiments which I had made, with the view of 

 ascertaining whether there was any augmentation in the 

 energy of the muscular or the proper current during the 

 act of contraction. All my efforts were useless, and I was 

 obliged to conclude that experiment did not prove that the 

 signs of the proper or muscular current acquired a further 

 degree of intensity during muscular contraction. 



We might believe in the development of electricity in- 

 dependently of the proper and muscular currents. But, 

 how can we suppose such a fact, when we see that the in- 

 duced contraction is transmitted through certain insulating 

 substances, such as turpentine, oil, &c., whilst it no longer 

 does so if we employ very thin leaves of mica. We might 

 suspect that electricity, developed during muscular contrac- 

 tion, acted by influence. In this hypothesis, we can under- 

 stand why turpentine offered no obstacle to the passage of the 

 contraction by induction ; but the other fact, that with an 

 extremely thin plate of mica, the same result does not 

 happen, makes it become doubly inexplicable. I have 

 tried the effect of covering a galvanoscopic frog, placed 

 on a glass plate, with a plate of mica; the discharge from 

 a Leyden bottle, passed between the knobs of the exitor 

 upon the mica plate, and contractions were excited in the 

 galvanoscopic frog. I shall not now stop to analyze this 

 fact: it is sufficient for the present to show, that induced 

 contraction through the mica ought to have occurred, if the 

 cause of the phenomenon resided in an electric discharge, 

 or was the result of the latter. I shall conclude by adding, 

 that I have endeavoured repeatedly, but always unsuccess- 

 fully, to excite contractions in the frog by holding the nerve 



