I extended an iron wire, two hundred and fifty feet in length, around my chamber, taking great care that it should not any where touch itself, and made its extremities to terminate at a table which I had prepared for the experiment. One of these extremities being brought into communication with a pile composed of fifty plates of copper and zinc, I held the other in my left hand, and with my right touched the summit of the pile. The Galvanism then proceeded from the bottom of the pile to the summit, traversing a portion of the arc formed by the animal machine. By the effect of this passage, we may therefore form some opinion of the celerity of the Galvanic current. Its rapidity was such, that neither I nor any of those who repeated the experiment publicly, were able to determine the degree. The truth of this proposition is confirmed by experiments lately made by the celebrated Van Marum, who charged large batteries by means of Galvanism.
PROPOSITION XIV.
The muscular contractions, which, according to the observations of Galvani, are produced by an electric atmosphere whether natural or artificial, correspond entirely with those produced by the pile, or by similar kinds of apparatus.
When a change of equilibrium takes place in those systems of bodies which communicate with the nerves and the muscles of the animal machine, it is always sensible of this change, and muscular contractions are produced.
EXPERIMENT I.
It is curious to see an animal, placed at the extremity of an apartment, experience a shock, when the electric spark is extracted at a considerable distance. I performed this experiment several times in the Cabinet de Physique of the Institute of Bologna, by means of a metal wire, not insulated, which was at the distance of four feet from the conductor of a common electrical machine. I repeated the experiment with crural nerves, having a ligature in the middle; and on extracting the spark, I observed violent contractions, which ceased when the ligature was formed at
the place of their insertion into the muscles. I then performed with the new apparatus of Volta the experiments which Galvani had made with artificial electricity alone. At first I employed several glass cups and piles of from one to two hundred plates of metal; which proved to me that similar results might be obtained with the following simple apparatus.
EXPERIMENT II.
Having placed upon a table two glass vessels filled with salt water, ([Plate II.] fig. 5.) which I connected by means of an arc composed of brass and zinc, I applied to the surface of the water, in one of the vessels, the spinal marrow of a prepared frog, the corresponding muscles of which I held in one of my hands. Another person with his hand, or a plate of metal, then touched the water contained in the other vessel, and, at each contact, the muscles experienced violent contractions. To remove all idea of the contractions being produced by the action of the salt water, I connected with the spinal marrow a part of the muscles of another animal, which, instead of the spinal marrow, was made to touch the salt water, and obtained the same result.