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. With respect to the single instance related by M. Cotugno, it is probable that both he himself, and all who have repeated experiments of this nature, must have been long ago convinced, that he was deceived into the belief of a shock, from the sensation produced by the struggles of the animal he dissected. That some kind of disagreeable sensation is occasioned by it, even in frogs, independent of that which must necessarily arise from irritation, and the contractions of their muscles, is evident from their restlessness, and expressions of uneasiness. In other animals, as I shall afterwards have occasion to shew, these expressions are still less equivocal: and, in man, we can ascertain both their degree and their kind. That they differ considerably from such as are produced by electricity, will be proved when I come to speak of the effects of this influence upon our senses. But the most important, and characteristic difference, which I have yet been able to discover, between this new influence and electricity, consists in their effects upon the contractile power of animals and of plants. The contractions of animals excited by electricity have a tendency to destroy that power upon which contractions depend. But the contractions excited, by the application of the metals, have, in all my experiments, had the directly opposite effect. The more frequently contractions have been, in this way, excited, the longer do they continue excitable: and the longer are the parts, upon which such experiments are made, preserved from putridity. An influence, capable of exciting contractions, without occasioning exhaustion, was a thing I so little expected to find, and so contrary to the character which had been given of this, both by Galvani and by Dr Valli, that I, at first, distrusted my own observation of the fact: but the number of comparative experiments, which I had afterwards occasion to make, though with views different from that of ascertaining the point in question, convinced me that this influence, so far from destroying the contractility of muscles, has a tendency to preserve it. Oxygene is, so far as I know, the only stimulus in nature, whose effects are at all analogous.