282 NERVOUS FORCE. LECT. XIV. XV. 



adherent is sufficient to interrupt the circulation of the proper 

 current. 



There is no doubt, then, that if the induced contraction 

 be propagated through a layer of one of these badly con- 

 ducting liquids, it is not owing to a current, which, taking 

 its source in the contracting muscle, would be able to diffuse 

 itself in the nerve of the galvanoscopic frog. 



Nevertheless, in considering the vast importance of these 

 experiments for the theory of this phenomenon, I was 

 anxious to try the effect of interposing between the muscle 

 in contraction and the nerve of the galvanoscopic frog, a 

 worse conductor than those just mentioned. The body 

 which appeared to me fit for employment in these experi- 

 ments, is the almost solid Venice turpentine, rendered more 

 or less liquid by the addition of a small quantity of oil of 

 turpentine. I varnished the thighs of a frog with this 

 mixture, and placed some of it on the nerve of the galvano- 

 scopic frog. After having arranged the experiment in the 

 usual way, I found that the induced contraction continued. 



To demonstrate the non-conducting power of the mix- 

 ture, I hasten to add, that if, in order to excite the contrac- 

 tions, I applied one pole of the pile upon the insulating 

 layer, well spread, without penetrating to the muscle itself, 

 and with the other pole touched the leg of the galvano- 

 scopic frog, no contraction was excited in the animal. 

 These experiments evidently prove, therefore, that induced 

 contractions exist through an insulating layer, capable of 

 intercepting not only the proper or muscular currents, but 

 even that of the pile which excites the inducing contrac- 

 tion. 



If the insulating mixture exceed certain limits in its 

 thickness, and if it have not a suitable degree of liquidity, 

 the induced contraction does not occur. It is impossible, 

 however, to state what degree of thickness and fluidity the 



