NATURAL HISTORY. 
yrged against this conclusion, that, 
Since metals are much better con- 
ductors of electricity than moist 
Substances, the charge of a muscle 
may be too weak to force its way 
through the latter, though it may 
be able to pass along the former ; 
my -answer is, that, in all Mr. 
Galvani’s experiments, the nerve 
makes a part of the connecting 
medium between the two surfaces of 
the muscle, and that the power of no 
compound conductor can begreater 
than that of the worst conducting 
substance, which constitutes a part 
} of it. 
It may be said, however, that, 
although there is no proof that any 
influence naturally resides in the 
nerves or muscles, capable of pro- 
ducing the effects mentioned by 
Mr. Galvani, these substances may 
still, by some power independent of 
the properties they possess in com- 
mon with dead matter, ‘contribute 
to the excitement of the influence, 
which is so well known to exist in 
them, after a certain application of 
metals. Before 1 enter upon the 
discussion of thissupposition, I must 
observe, that there are two cases of 
such an application of metals: the 
firstis, when we employ oualy one 
metal ; the secon’, when we employ 
two or more. iil respect to the 
first case, a Jate author, Dr. Fowler, 
who seems to have made many ex- 
periments relative to this point, po-- 
sitively asserts, that he never saw a 
fair instance of motion being pro- 
duced by the mere application of a 
single metal to a muscle and its 
nerve. I shall, therefore, defer 
treating this case, till I speak of the 
conditions which are necessary for 
the excitement of the influence. Nor 
will the present subject suffer from 
‘this delay; for if it be shewn, as I 
[*63 
expect it will, that, when two or 
more metals are used, the muscle and 
its nerve do not furnish -any thing 
but what every other moist substance 
is equally capable of doing, it will, 
I think, be readily granted, that 
they can give nothing more, when 
only one metal is applied to them. 
In regard to the second casey 
Mr. Volta has affirmed, or has said 
at least, what I regard as equivalent 
to affirming, that, when two metals 
are employed, the influence in ques- 
tion is excited by their action upon 
the mere moisture of the parts which 
they touch. The proofs, however, 
of this assertion were reserved for 
some future communication. But 
as more than two years have now 
elapsed since they were promised, 
and none have been given to this 
society, or have appeared, as far as 
Ican learn, in any other way, I 
hope I shall not be thought preci« 
pitate, if, at this distance of time, 
I offer one of the same point, which 
seems to me both plain and decie 
sive. 
It is known, that, if a muscle 
and its nerve be covered with two 
pieces of the same metal, no motion 
will take place upon connecting 
those pieces,by means of one or more 
different metals. After making this 
eXperiment one day, I accidentally 
applied the metal I had used as the 
connector, and which I still held in 
one hand, to the coating of the mus- 
cle only, while with the other hand 
I touched the similar coating of the 
nerve, and was surprised to find that 
the muscle was immediately thrown 
into contraction. Haring pro 
duced motions in this way sufficient- 
ly often to place the fact beyond 
doubt, I next began to consider its 
relations to other facts formerly 
knowm I yery soon perceived, that 
the 
