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

by Richard Fowler

We are told by Mr Cavendish, that Mr Walsh found the shock of the torpedo would not pass through a small brass chain: but the influence discovered by Galvani, passes, without sensible diminution of its effects, through a small brass chain of several inches in length, when it is drawn so tight as to bring its links into close contact with each other: and it passes through a gold chain when held between two persons, and suffered to hang with a considerable bend. Yet, if we may be allowed to judge of the comparative strength of the two influences, by the effects which they produce upon animals, that of the torpedo must certainly be allowed to be the strongest; and I see no other way of accounting for its finding an insuperable obstacle to its transmission, where the other finds scarcely any, except by supposing that they are in reality different in their nature.

Dr Valli tells us, that he observed the hairs of a mouse, attached to the nerves of frogs by the tin-foil, with which he surrounded them, alternately attracted, and repelled by each other, whenever another metal was so applied as to excite contractions in the frogs.

This experiment I have many times repeated, both in the manner described by the Dr, and with every variation in the disposition of the hairs which I could devise: but whether they were placed upon the metals, the nerves, or the muscles, or upon all at the same time, neither I, nor my friends who assisted me, have in any instance been able to observe them agitated in the slightest degree.

I have made similar experiments upon a dog, and upon a large and lively skate, by disposing, in the same way that I did the hairs of a mouse, flakes of the finest flax, swansdown, and gold leaf; but although the contractions produced in the skate, by the contact of the metals, were so strong as to make the animal bound from the table, not the least appearance of electricity was indicated.

I next suspended, from a stick of glass fixed in the ceiling of a close room, some threads, five feet in length, of the flax which I used in the former experiment; and approached some frogs, recently killed, and insulated upon glass as near to them as was possible, without touching: but the threads were in nowise affected by the contractions produced in the frogs.

In this respect, therefore, this influence agrees with that of the torpedo, &c. So far as I know, M. Volta’s instrument for collecting, condensing, and rendering sensible, very small degree of electricity has not been employed in the examination of either.

And indeed I am not sure, if, in examining the newly discovered influence, by such a test, a sufficient quantity of electricity might not be produced merely by the motion of the animals, subjected to the experiment, to occasion some fallacy in the result. Certain, however, it is, that although this influence did not affect the electrometer in these experiments, it produces infinitely stronger effects upon an animal, than any which can be produced by a quantity of electricity sufficient to affect an electrometer to a very high degree. I have frequently detached the crural nerves of frogs for some length; and having supported them upon a rod of silver, have applied an excited piece of glass, or sealing wax, to the whole length of this rod. The coarsest electrometers have been effected by it, at considerable distances: but I have never, in this way, been able to excite contractions, unless by laying the rod upon the excited cylender of a powerful electrical machine.

This new influence likewise resembles that of the torpedo, in producing its effects almost equally well, when both it and the subject upon which it acts are insulated from surrounding conductors. But an experiment similar to that, which I have related, of insulating, and positively electrifying, both the frog and the metals applied to it, has never (so far as I am acquainted,) been tried with the torpedo.

Both these influences agree too, in not producing so strong an effect, when the subject, upon which they act, is immersed in water, as when it is in the open air. When the separated leg of a frog was held under water, and formed part of the circuit through which this, to influence, had to pass, in order to excite another leg; it never contracted, although it did, and strongly, when held above the surface, as I have already had occasion to notice. And we are told by Mr Walsh, that the shock of the torpedo was four times stronger in air, than when given under water.

This influence differs, both from that of the torpedo, &c. and from electricity, in producing no sensation (in man at least,) at all similar to that from an electrical shock.