LECT. XIV. XV. INDUCED CONTRACTIONS. 281 



of the thighs of the first frog. I always used, in order to 

 excite the contractions, a small pile of Faraday's of five 

 elements immersed in pure water, and the conductors of 

 which are varnished and covered with silk. 



No other liquid among the number with which I experi- 

 mented, prevented the induced contraction from taking 

 place. The liquids which I employed, and through which 

 the phenomenon appeared, were water, slightly acidulated 

 or salt water, serum, olive oil, diluted alcohol, resinous 

 spirit varnish, and oil of turpentine. I generally let fall a 

 few drops of the liquid I wished to try, upon the muscle, 

 and I moistened with the same liquid the nerve of the gal- 

 vanoscopic frog. The induced contraction was also pro- 

 duced when we interposed a piece of filtering paper, dipped 

 in the same liquid, between the muscle and the nerve. 



The slight conducting power of some of these liquids, 

 such as oil, spirit of turpentine, varnish, &c., leads me to 

 suspect that the induced contraction was not destroyed by 

 the interposition of a perfectly insulating body. 



I have satisfied myself, in fact, that through even very 

 thin layers of these liquids, the proper current and the 

 muscular current are not propagated. It will be, doubtless, 

 remembered, that when we take a galvanoscopic frog in 

 the hand, and put its nerve in contact with moistened 

 paper, which is in some way in communication with the 

 ground, contractions are produced. The same phenomenon 

 is observed by touching the muscles of a frog or other ani- 

 mal, which communicates with the ground, with the nerve 

 of the galvanoscopic frog. In all these cases, it is the 

 proper current which circulates through the experimentor, 

 the ground, the body touched, and the frogs ; but if we 

 plunge the nerve of the latter in oil, oil of turpentine or 

 varnish, the slight layer of these liquids which remains 



