The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

78 VOLTAIC ELECTRICITY.
well produced by making a metallic communication between
the outside muscle and crural nerve. He did not for one moment suppose that the manifestation of electricity was the
result of the chemical action upon the metals.
Galvani had previously entertained notions respecting the
agency of electricity, in producing muscular action: these new
experiments, therefore, as they seemed to favor his views, had
with him more than ordinary interest. He immediately
ascribed the convulsive movement in the limb to electrical
agency, and explained them by comparing the muscle of an
animal to a Leyden vial, charged by the accumulation of
electricity on its surface, while he imagined that the nerve
belonging to it performed the function of a wire, communicating
with the interior of the vial, which would, of course, be
charged negatively. In this state of things, if a communication by a good conductor were made between the muscle and
nerve, a restoration of the electric equilibrium, and a contraction of the fibres, would ensue.
It is curious to notice how frequently the progress of discovery in the sciences is influenced by fortuitous circumstances,
and in no case is it more striking than in the present. Had
G-alvani been as good an electrician as he was anatomist, it is
probable that the convulsions of the frog would have occasioned
him no surprise; he would immediately have seen that the
animal formed part of a system of bodies under induction, and
he would have considered the movements of the limbs of the
frog, as evidence of nothing more than a high electroscopic
sensibility in its nerves.
To perform the experinent with the frog's legs successfully,
the legs of the frog are to be left attached to the spine by the
crural nerves alone, and then a copper and a zinc wire being
either twisted or soldered together at one end, the nerves are
to be touched with one wire, while the other is to be applied
to the muscles of the leg. Figure 1 shows the arrangement.
There are several ways of varying this experiment. If a
piece of copper, as a penny, be laid on a sheet of zinc, and if a
common garden snail be put to crawl on the latter, he will be
observed to shrink in his horns and contract his body whenever
he comes into contact with the penny: indeed, after one or
two contacts he will be observed to avoid the copper in his
journey over the zinc.
The experiments of Galvani excited much attention among
the men of science of that period: they were repeated and
varied in almost every country in Europe, and ascribed to various causes. Some imagined them the effect of a new and