I HAVE farther observed, that although the previous application of a second plate of Silver to one half of the plate of Zinc, does not prevent the Flash when the other half of the plate of Zinc, touching the Tongue, is brought into contact with the first piece of Silver placed between the lip and the gum; yet if the Zinc and Silver are in the first place applied to each other, then placed between the lip and gum, and, after this, touched with the Tongue, there is no appearance of a Flash, although some degree of pungency and a disagreeable sensation is perceived by the Tongue: and a mixed mass, composed of one part of Zinc and two parts of Quicksilver, or a mass composed of three parts of Zinc and one of Silver, incorporated in a furnace, have not the effect, when they are applied to Nerves, of exciting convulsions of the Muscles in which the Nerves terminate. I HAVE also found, that two thick pieces of raw or boiled flesh, one between the Zinc and Tongue, and the other between the Silver and Tongue, do not prevent the disagreeable pungent sensation when the two Metals touch: and, in like manner, that the interpolation of two pieces of flesh between the Zinc and Tongue, and between the Silver and the upper Lip, does not prevent the appearance of a flash, on bringing the two Metals into contact. 19. I PUT a very thick plate of Zinc into a vessel with water, and placed, near to it, in the water, the under part of the Spine and the hind Legs of a Frog, after cutting all the parts at the Pelvis except the Sciatic Nerves. I then touched the Zinc with a gold Probe, and found, that, when I touched that part of the Zinc which was above the water, the Legs of the Frog were not affected; but when I touched that part of the Zinc which was below the surface of the water, the Legs of the Frog were convulsed[13]. I NEXT put into the water one of the hind Legs of a dead Frog, and its other Leg into an adjoining vessel with water. Into the opposite side of the second vessel, I put one of the hind Legs of a living Frog, in which all the parts at the Pelvis, except the Sciatic Nerves, were cut; and into a third glass vessel with water, I put its other Leg. When I now touched that part of the Zinc, which was below the surface of the water with a gold Probe, the Legs were not convulsed; but, if I, at the same time, dipped the finger of my other hand into the water contained in the third vessel, they were convulsed: when, instead of my finger, I dipped into the water a stick of sealing-wax, held in my other hand, the Legs were not convulsed. I FOUND, by the three following Experiments, that the Muscles are convulsed, whether the Influence, produced by the application of the Metals, passes upwards or downwards along the Nerves. 20. I CUT four living Frogs transversely at the middle part of their Spines, and threw away the fore parts of their Bodies and their Abdominal Viscera.