3. The arguments against the antiquated doctrine of transudation, through parts of a living body, are already so numerous and satisfactory, that it may be thought unnecessary to notice in this place, a decisive one so far as relates to the skin of frogs, at least, which may be deduced from the fact already mentioned; that so long as the skin was suffered to remain upon the limbs of frogs, placing them in water, very evidently preserved the contractility of their muscles, whereas when the skin was taken off, the muscles became hard, and incapable of contracting, in a very few hours. Had there been a possibility of water soaking through the skin, this difference could not possibly have had place. 4. In speaking of some of the relations, which subsist between the influence discovered by Galvani and the nerves, I omitted mentioning the following facts. A very different effect is produced by applying the metals to the brain or spinal marrow of frogs, from what is produced by applying them to their nerves. In the latter case, I have observed, that every muscle, to which a nerve below the part touched is distributed, is brought into instant contraction. But no muscles are brought into contraction, when the metals are applied to the brain or spinal marrow, except such as derive their nerves from the part immediately in contact with the metals. The influence does not stimulate or pass along the spinal marrow, as it would along the trunk of a nerve, to affect all other nerves branching off from it.