The American Electro Magnetic Telegraph: With the Reports of Congress, and a Description of All Telegraphs Known, Employing Electricity or GalvanismVail, Alfred
History
The American Electro Magnetic Telegraph: With the Reports of Congress, and a Description of All Telegraphs Known, Employing Electricity or Galvanism
Vail, Alfred
Telegraph -- History
“It happened in the year 1790, that his wife, being consumptive, was
advised to take, as a nutritive article of diet, some soup made of
the flesh of frogs. Several of these animals, recently skinned for
that purpose, were lying on a table in the laboratory, close to an
electrical machine, with which a pupil of the Professor was amusing
himself in trying experiments. While the machine was in action, he
chanced to touch the bare nerve of the leg of one of the frogs with
the blade of the knife that he held in his hand; when suddenly the
whole limb was thrown into violent convulsions. Galvani was not present
when this occurred, but received the account from his lady who had
witnessed, and had been struck with the singularity of the appearance.
He lost no time in repeating the experiment: in examining minutely
all the circumstances connected with it, and in determining those
on which its success depended. He ascertained that the convulsions
took place only at the moment when the spark was drawn from the prime
conductor, and the knife was at the same time in contact with the
nerve of the frog. He next found that other metallic bodies might be
substituted for the knife, and very justly inferred that they owed
this property of exciting muscular contractions to their being good
conductors of electricity. Far from being satisfied with having arrived
at this conclusion, it only served to stimulate him to the farther
investigation of this curious subject; and his perseverance was at
length rewarded by the discovery, that similar convulsions might be
produced in a frog, independently of the electrical machine, by forming
a chain of conducting substances between the outside of the muscles
of the leg, and the crural nerve. Galvani had previously entertained
the idea, that the contractions of the muscles of animals were in some
way dependent on electricity; and as these new experiments appeared
strongly to favour this hypothesis, he with great ingenuity applied it
to explain them. He compared the muscles of a living animal to a Leyden
phial, charged by the accumulation of electricity on its surface, while
he conceived that the nerve belonging to it, performed the function of
the wire communicating with the interior of the phial, which would, of
course, be charged negatively. In this state, whenever a communication
was made by means of a substance of high conducting power between
the surface of the muscle and the nerve, the equilibrium would be
instantly restored, and a sudden contraction of the fibres would be the
consequence.
Public-domain text, read in full here on John Shaqi.
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