HISTORY OF GALVANISM. 5 



very decisive marks of electricity, where none 

 could be detected by Bennet's gold-leaf elec- 

 trometer. 



After employing the electric fluid, as disengaged Discovery 

 from the common machine, Galvani next tried the g a i?LnUm. 

 atmospherical electricity ; and it was in pursuance 

 of this object, that he was first led to observe 

 the effects of galvanism properly so called. Hav* 

 ing suspended a number of frogs by metallic hooks 

 to an iron railing, he found that the limbs were 

 frequently thrown into convulsions, when it did 

 not appear that there was any electricity in the 

 atmosphere. Having duly considered this pheno- 

 menon, he discovered that it did not originate from 

 an extraneous electricity, but that it depended 

 upon the position of the animal, with respect to 

 certain metallic bodies. 



It appeared, that when the muscle and nerve Action of 

 of a frog were each in contact with metallic bodies, 

 and these were also connected by a metal, the 

 contractions were always produced. The effect 

 was considerably increased by arming the nerve 

 with a metallic coating, by which means a larger 

 portion of it was brought into contact with the 

 metal. But the most important of Galvani's dis- 

 coveries was the effect produced by the combina- 

 tion of two metals. Of these combinations the 

 most powerful was that of zinc and silver ; and 

 the most violent convulsions ensued when the 

 nerve was coated with one of these metals, the PLATE i. 

 muscle placed in contact with the other, and the Fts ' 9 * 



