An Account of the Late Improvements in Galvanism. Giovanni Aldini
XV.
Opium, cinchona, and other stimulants of a similar kind, which exercise a powerful action on the animal machine, contribute also to excite the action of the pile.
EXPERIMENT I.
In the last sitting of the Institute of Bologna, at which I was present, I constructed two piles, each composed of fifteen pieces of silver and zinc, employing for the one an extract of opium, and for the other an infusion of cinchona in alcohol. I covered the piles with two equal receivers; formed an insulated plenum, by pouring mercury around the bottoms of them; and placed weights on the receivers sufficient to prevent the mercury from raising them. At the end of some hours, I found a remarkable elevation of the surface of the mercury, so that the receivers remained fixed without requiring any weight to keep them down. In the bell which covered the pile where extract of opium had been employed, the mercury rose more than an inch; but in that covering the other, where cinchona had been used, the elevation of the mercury was scarcely three lines.
EXPERIMENT II.
Having successively introduced a taper into each of the two receivers before mentioned, it was immediately extinguished in that containing the pile with the extract of opium; but in the other containing the pile with the infusion of cinchona, it continued burning for some time. I found also that four of the plates, at the bottom of the pile where I employed opium, had suffered from the action of the mercury; and that some others, to the height of about three inches and a half, exhibited a few globules of that metal. The pile in which I employed infusion of cinchona showed scarcely any signs of the action of the mercury.
EXPERIMENT III.
As I concluded that the pile in which I had employed the alcoholic extract of opium possessed more activity than the other, I examined it for four or five days successively. I tried the flame of a taper with the same result as before, and assured myself that this pile retained the Galvanic power, though a little weakened, even till the eighth day. On the other hand, twenty-four hours had scarcely elapsed, when the pile in which alcohol and cinchona had been employed exhibited no signs of activity.
EXPERIMENT IV.
I constructed two piles, in the same manner, with pieces of pasteboard interposed, which had been previously moistened with strong solutions of camphor and of castor oil, in pure alcohol. In these two piles the Galvanic effects were much weaker in every respect than those observed in the preceding experiment; for, besides the explosion being less, the elevation of water in the insulated plenum was very small, and the alteration of the flame was scarcely sensible.
EXPERIMENT V.
I was able to convince myself that the effects of the two piles, before mentioned, were the immediate result of the substances dissolved, and not of the alcohol; for, having constructed a pile of thirty plates of silver and zinc, with pieces of pasteboard interposed, moistened with pure alcohol, I observed no signs of Galvanism; and the case was the same when I employed a pile of zinc combined with copper and other metals.
PROPOSITION XVI.
If the general relation between Galvanism and electricity be examined, such a correspondence will be found between them, as tends to confirm the analogy already stated.
To illustrate this proposition, I shall here take a view of the particular properties of electricity and Galvanism, which, if considered separately, would not be sufficient for my object. I am, however, of opinion, that when combined together they will serve to prove it in a satisfactory manner.
1st, Galvanism, like artificial electricity, emits sparks, fuses metals, and can even be employed to charge armed non-conducting bodies. I have proved the last-mentioned property, discovered by the celebrated Van Marum, with a new apparatus, composed of a pile with a hole in the middle, in which I place the flask I intend to charge.
2dly, The influence of artificial electricity tends to accelerate the putrefaction of animal parts; and the same phænomenon may be produced by communication with the Voltaic pile, or by the first processes of Galvani.
3dly, The electricity of the Leyden jar is renewed in part immediately after its discharge. A similar phænomenon is exhibited by the pile; and it is observed, if the common Galvanic armatures be employed, that the vital force in animals is almost revived, when the arcs are applied different times.
4thly, As the action of common electricity and of the pile is suspended, when the combination of the metallic pieces is changed; in like manner, in a system of several animal machines, if their combination be changed, muscular contractions entirely cease.
5thly, Water may be decomposed by common electricity, as well as by the Galvanic pile, according to the ingenious method proposed by Dr. Wollaston. I lately saw, with the greatest pleasure, experiments on this subject performed by himself with the utmost neatness and precision. It is much to be wished, that the same result could be obtained by animal Galvanism alone; as it might tend to throw great light on some important points in physiology. For my part, I entertain no doubt that, after repeated trials, it may one day be effected, by means of large animals possessing a great abundance of animal electricity.
To conclude: I think I may venture to assert, that the correspondence between the properties of Galvanism and common electricity might be carried to a much greater extent, in confirmation of the analogy which I proposed to prove in this proposition.
PROPOSITION XVII.
The hypothesis of an animal pile, analogous to that formed artificially, seems well calculated to explain the sensations and contractions in the animal machine.
It seems to be proved by the observations of Mr. Davy, Professor in the Royal Institution of Great Britain, and those of M. Gautherot at Paris, that a pile may be composed without any metallic substances whatever. We are therefore naturally led to suppose, that one may be composed also of animal substances alone. Though this has never yet been obtained by art, we behold it with admiration constructed by nature in various animals. If we examine, indeed, the structure of the regular bodies which succeed each other in the torpedo, the electrical eel of Surinam, and in the silurus, we shall find them to be real animal piles, differently arranged: and if an animal pile, exceedingly strong, be capable of communicating a shock, why should not one of a more moderate nature excite that activity which is necessary to produce muscular convulsions? I have already proved, that the system of the nerves and that of the muscles possess different Galvanic powers, or, as it were, different kinds of electricity, to which the animal moisture serves as a conductor. In this point of view, the discovery of the pile of the celebrated Volta, instead of destroying the principle of Galvanism, tends rather in a powerful manner to support it. The object of Galvani’s system is to prove the existence of an animal electricity, and then to explain how its action operates in producing muscular sensations and contractions. The first part of his system rests upon facts, the truth of which neither time, nor the different experiments made by philosophers, have been able to weaken. The second presents an hypothesis which, perhaps, may be further illustrated when the physiology of the human body is better known. Galvani, to explain the activity of animal electricity, supposes the nerves and muscles to be like the Leyden jar; and this idea I confidently adopted. But by the expression ‘Leyden flask’ he meant nothing else than that in the animal machine there are two opposite kinds of electricity, resulting from the nervous and the muscular systems, to which animal moisture continually serves as a vehicle. It was in this sense that he announced his theory of the Leyden flask, in his public lectures, and in his last works. No better comparison was then known, in the language of philosophy, to express this action. It however affords me great pleasure, that I can now substitute for it the pile discovered by Volta, which is perfectly consistent with the system of Galvani; and since I am ready to allow that the invention of the metallic pile gives Volta a title to the discovery of metallic electricity, I hope the discovery of animal electricity, properly so called, will be allowed to Galvani, as similar phænomena are exhibited by the nervous and muscular systems, independently of common electricity.
But some important questions in regard to Galvanism still remain to be answered, such as the following: whether the