Dr. Wells's Observations on an Influence, & c. 247 
When a muscle contracts upon a connection being formed, 
by means of one or more metals, between its external surface 
and the nerve which penetrates it, Mr, Galvan 1 contends 
that, previously to this effect, the inner and outer parts of the 
muscle contain diiferent quantities of the electric fluid that 
the nerve is consequently in the same state, with respect to 
that fluid, as the internal substance of the muscle; and. that 
upon the application of one or more metals between its outer 
surface and the nerve, an electrical discharge takes place, 
which is the. cause of the contraction of the muscle. In short, 
he supposes a complete similarity to exist between a muscle, 
in a proper condition to exhibit this appearance, and a charged 
Leyden phial ; the nerve of the former answering, as far as 
his experiments are concerned, the same purpose as the wire, 
which is connected with the internal surface of the latter. 
Now, if this were just, such a muscle ought to contract, 
whenever a communication is formed between its internal sur- 
face and the nerve, by means of any conductor of electricity ; 
and accordingly Mr. Volta, who to a certain extent adopts 
Mr. Galvani's theory, asserts this to be the case, as often as 
the experiment is made upon an animal which has been 
newly killed. But I am inclined to believe that he rests this 
assertion upon some general principle, which he thinks estab- 
lished, and not upon particular facts ; for he gives none in 
proof of it, and I have often held a nerve of an animal newly 
killed in one hand, while with the other I touched the muscle 
to which the nerve belonged, but never saw contractions by 
this means excited. I have also frequently taken hold of a 
nerve of an animal, which was recently killed, with a non-con- 
ductor of electricity, and have in this way applied its loose 
Kk 2. 
