Experiments and Observations Relative to the Influence Lately Discovered by M. Galvani and Commonly Called Animal Electricity

by Richard Fowler

This argument appears, to me, to do away all support, which the hypothesis may seem to derive from the experiment, before quoted, of applying the metals equally to both sciatic nerves, after one of them had been divided; I may however remark, that the pain necessarily excited by arming a nerve, whose communication with the brain was not interrupted, would fully account for the more rapid exhaustion of the muscles, to which it belonged, compared with such as had not been acted upon by so strong an additional stimulus. As fact, however, is always more satisfactory than argument, I shall relate the following accidental experiment, in proof of the relevancy of the foregoing observation.

Four days after I had divided the crural nerve of a female frog, full of spawn, I found her dead; she had been observed alive the night before. The application of the metals to the leg, whose nerve had not been divided, did not excite the slightest contractions, but on applying them to the leg, in which the nerve had been divided, tolerably strong contractions were excitable, for more than twelve hours after she was found. The spawning season had closed, upwards of a week before this happened, and, as this frog had long been without a male to assist her, it is probable, that her death had been occasioned by the retention of her spawn, as it was found in a very dissolved state. The pain, necessarily preceding such a death, could affect the different parts of the animal, only through the medium of its nerves; and hence the exemption of that part from its effects, to which the communication, by nerve, had been interrupted.

The same observation will apply to that argument, which Dr Valli has drawn, in support of his hypothesis, from the practice of fishermen. By destroying the brain, they take away all sense of pain, and, consequently, preclude that exhaustion which is so notorious for disposing to putridity.

Should it, therefore, be ever proved, that the phenomena discovered by Galvani are effects of the action of electricity, I cannot think Dr Valli’s hypothesis will be deemed a satisfactory account of the manner in which it produces them.

Strong, however, as is the analogy, which, in many particulars this influence bears to electricity, considerable doubts must, I think, still remain as to their identity.

The grounds of these doubts would best appear in an accurate and full statement of the several points, both of resemblance and of difference between this influence, electricity, and that power which distinguishes the torpedo, the gymnotus, and the silurus; but, I can here promise no more than a very imperfect and desultory sketch of these.

In order to accumulate artificial electricity, if I may be allowed the use of such an expression, it seems necessary, that there should be motion between two substances, an electric and a conductor. But, neither motion nor electrics have any share in the production of that influence which occasions the phenomena in question. The motion, here, is the effect, and not the cause of the accumulation: and instead of one conducting substance of any kind whatever, two metallic substances seem indispensably requisite[^[9]].

That influence, whatever it be, which is possessed by the torpedo, &c. seems to depend entirely upon the will of these animals, both for its production, and management, as appears not only from the retraction of their eyes within their sockets, whenever they mean to give a shock, but, likewise, from each shock being increased, diminished, or withheld, as they are irritated or aware of some obstacle to its transmission. But the will of an animal has no share in the production of the phenomena discovered by Galvani.

In the scale of conductors of electricity, charcoal holds a higher place than the fluids of animal bodies, and ice than the metallic salts. But of the influence in question, I have found animal fluids, and metallic salts, excellent conductors, at the same time that I have never observed it pass through charcoal, or even dried wood. I have, likewise, reason to believe that it does not pass through ice. Ice, indeed, is but a very imperfect conductor of electricity, when free from air bubbles, and when the experiments with it are made in a very low degree of temperature. Yet we are told by Mr Achard, that it will conduct electricity, even when Reaumur’s Thermometer stands at 6 degrees below 0.

But the temperature of the room, in which I made my experiments, was at least 55 degrees above 0, by Fahrenheit’s scale. I may likewise remind the reader of the experiment, in which the abdomen of a frog was filled with mercury, and a rod of silver passed through it to the sciatic nerves. A piece of zinc, touching both mercury and silver, excited no contractions; whereas most vigorous ones were excited when water was substituted for the mercury. A proof, as I take it, that water is a much better conductor of this influence than mercury: but of electricity, mercury is deemed a better conductor than water.