An Account of the Late Improvements in Galvanism. Giovanni Aldini
kinds of electricity, it would seem that, by communicating to them any electricity, the electricity of the whole apparatus ought to have been reduced to the same kind; consequently that no shock ought to have been produced. The contrary, however, was the case. We experienced very strong shocks, very little different from those which would have been obtained without artificial electricity. I observed the same result with the pile.
EXPERIMENT II.
An insulated torpedo being electrified, the shocks it gave were not increased. The torpedo was killed, and then armed, according to the method of Galvani, for the purpose of trying whether metallic electricity, in this case, would have any influence over it. After this arrangement was made, every time that the conducting arc was applied to it strong contractions were produced; but very little different from those remarked in other animals. This observation is agreeable to those made at Naples by the celebrated Abilgaard, who, having subjected the torpedo to the Galvanic processes, found no extraordinary contractions.
PROPOSITION XII.
The Galvanic action is increased by employing as part of the arc the apparatus of Volta, or the electrified Leyden flask.
EXPERIMENT I.
In the hall of the Institute, I placed on a large table a hundred glass cups, and arranged them in such a manner as to form two rectangles, each composed of fifty. I established a communication between the first of these cups and the apparatus of Volta, by means of a metallic wire, which proceeded from one of the interior chambers of the Cabinet de Physique, and terminated at the place where the experiment was performed. I then tried this arrangement several times; and, however different opinions might be in regard to the precise increase of the action of the Galvanism, all constantly agreed in considering the shock as stronger. Some even went so far as to assert that it was increased a third.
It gave me great satisfaction to be able, on this occasion, to confirm the last discovery of Professor Volta, as well as one of those which he had made before. One observation, well attested, which tends to establish the truth of this proposition, is, that if a person touch the summit and base of the pile with two large metallic conductors, the shocks he receives will be much stronger.
EXPERIMENT II.
Electricity, concentrated in the Leyden flask, contributes also to increase the action of Galvanism. Having prepared a pile, composed of fifty plates of copper and zinc, I formed an arc by interposing a charged jar, and obtained an explosion much stronger than that obtained by the Leyden flask charged with an equal quantity of the electric fluid, and discharged independently of the pile.
EXPERIMENT III.
I took the same flask, after it was discharged, and having formed a portion of an arc, applied to the two extremities of the pile, I observed that the Galvanism refused to pass the obstacle presented to it by the stratum of glass interposed between the two coatings; consequently I received no shock.
EXPERIMENT IV.
I repeated the second experiment, insulating the pile, and at the same time the person who touched the pile with the charged flask. By these means I obtained a much stronger explosion than could have been produced separately by the Leyden flask or the pile. In this experiment I observed that the repeated passage of the electricity of the flask throughout the whole extent of the pile, did not deprive it of the property of exciting Galvanism.
PROPOSITION XIII.
Galvanism, in animals and in the pile, traverses large spaces with the same rapidity as the electric fluid.
EXPERIMENT.
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.
EXPERIMENT III.
The same apparatus being retained, if either the person who touches the surface of the water in the first glass vessel, or the part of the frog immersed in the second, be insulated, no muscular contractions are produced; but they again take place when the insulation is removed. The violence of the contractions is increased by increasing the number of the glass vessels. If these vessels are made to communicate by means of arcs, formed of one homogeneous metal, the results are not different from those observed when heterogeneous metals are employed.
EXPERIMENT IV.
Being desirous to confirm the theory of the Galvanic atmosphere, I placed in it the body of an executed criminal. I removed the pile to the distance of a foot from the trunk, without the usual communication of metallic arcs; and having made an incision in each ancle, two persons held two frogs prepared in the usual manner, in such a position that the spinal marrow rested on the incisions. When matters were thus arranged, every time that a third person touched the summit of the pile, both the frogs experienced violent contractions, and to such a degree, that, leaving free one of the extremities, a real electrico-animal alarum was obtained, perfectly similar in its effect and identity to that described by Galvani in his Commentary. When the metallic apparatus is employed, if one of the persons who holds a frog be insulated, the frog will remain motionless, while the other will experience the usual effect. I had an opportunity of confirming the truth of this observation, on the trunk of a dog, during a course of experiments made in the Hôpital de la Charité, at Paris, and at St. Thomas’s Hospital, London.