HISTORY OF GALVANISM. 



have not been found to succeed in the hands of 

 other experimentalists. One important fact, how- 

 ever, he may be considered as having established, 

 that contractions can be excited in an animal by 

 placing the nerves and the muscles in certain 

 situations with respect to each other, without em- 

 ploying any metallic substance ; a fact which was 

 afterwards brought forward in a very striking 

 manner by Aldini, but which appears still to be 

 involved in a degree of mystery, both as to the 

 nature of the operation itself, and as to the class 

 of physical phenomena to which it ought to be 

 referred. 



Voita's Volta continued to be actively engaged in pro- 



secuting his inquiry into the nature of galvanism, 

 and in perfecting the hypothesis that he had 

 formed, to explain the operation by which it is 

 excited. He now introduced a new principle into 

 his theory, and found it necessary to alter the 

 terms in which he had announced it, particularly 

 with respect to the circumstances requisite for the 

 extrication of the electric influence. He had 

 before stated that two metals were essential to this 

 purpose ; but he now informs us that, provided the 

 substances diifer in their power of conducting 

 electricity, their metallic nature may be dispensed 

 with. He divides conductors into the two classes 

 of the dry and the moist ; the first including 

 metals and charcoal; the latter essentially consist- 

 ing of water, holding various substances in solu^ 

 tion. In order to form a galvanic circuit, it is ne- 



