When a frog has been long dead, I have been sometimes more than a quarter of an hour without being able to excite a single contraction by the application of the metals: but after this, without at all varying the means employed, contractions have appeared, and have become gradually more and more vigorous. It is said, (for I have never had an opportunity of making the experiment,) that a stream of electricity passed through a sensitive plant produces an almost immediate collapse of its leaves. But the influence, discovered by Galvani, produced no such effect in the following experiment. Having separated the leg of a frog from its body, I freed its crural nerve from surrounding parts, and with one hand held it supported upon the end of a probe. An assistant placed a piece of silver under its foot, and held the zinc with which it was to be touched. A sensitive plant formed the medium of communication between us. He held the bottom of its stem between his fingers, while I held the top: so that when the silver was touched by the zinc, the influence passed up the plant, and through the whole of its stem. The frog’s leg instantly contracted, and repeated its contractions every time the silver and zinc were in contact: but the leaves of the plant did not collapse; neither did they when any of its branches formed part of the circuit. I must, however, confess that the plant, upon which this experiment was made, had been kept through the winter. With a young one the result might possibly be different; but such an one I have not yet had it in my power to procure. The torpedo does not appear at all affected by the influence which itself produces. Animals, in which Galvani’s phenomena are produced, are strongly affected. From this circumstance, and still more from the presence of metals being absolutely requisite to their production, some may be induced to believe, that the influence, which causes them, is something external to animals; and that it arises from the mutual contact of the metals only. I must confess I was, for some time, inclined to entertain this opinion; and its probability appeared to be not a little increased by observing that its effects differed with the metals employed, and were strongest when their surfaces were extended, and applied horizontally to each other. I began, therefore, to suspect that it might be some hitherto undiscovered property of metals; for that it was not an electrical phenomenon, seemed still further proved by the circumstance above related. It has been demonstrated, by the very interesting discoveries of M. Volta, that, ‘wherever the capacity of holding electricity is greater, there the intensity of electricity is less’:--‘and that the capacity of a conductor is increased, when, instead of remaining quite insulated, the conductor is presented to another conductor not insulated; and this increase is more conspicuous, according as the surfaces of those conductors are larger, and come nearer to each other[10].’