GALVANISM, OR VOLTAIC ELECTRICITY.
“To play with fire
They say is dangerous; what is it then
To shake hands with the lightning, and to sport
With thunder?”—Tyler.
Galvanism, or electricity of quantity, in contradistinction to frictional electricity, called electricity of intensity, owes its name to the experiments on animal irritability made in 1790 by M. Galvani, a professor of anatomy at Bologna. These experiments were suggested by the following circumstances.
ORIGIN OF GALVANISM.
It happened that the wife of Galvani, who was consumptive, was advised to take as an article of food some soup made of the flesh of frogs. Several of these creatures were killed and skinned, and were lying on the table in the laboratory close to an electrical machine, with which a pupil of the professor was making 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 had in his hand, when suddenly the whole limb was thrown into violent convulsions. Galvani was not present when this occurred; but being informed of it, he immediately set himself to investigate the cause. He found that it was only when a spark was drawn from the prime conductor, and when the knife or any other good conductor was in contact with the nerve, that the contracting took place; and after a time he discovered that the effect was independent of the electrical machine, and might be equally well produced by making a metallic communication between the outside muscle and the crural nerve.
SIMPLE EXPERIMENT TO EXCITE GALVANIC ACTION.
If the young experimenter will obtain a piece of zinc of the size of half a crown and place it on the top of his tongue, and place a half-crown underneath it, and bring the edges of the half-crown and zinc in contact in front of his tongue, he will notice a peculiar sensation in the nerves of this organ, and some taste will be imparted to his mouth at the moment of contact.
WITH METAL PLATES IN WATER.
