3. Contractions may be produced in the prepared limb of a frog, by putting it in water, and then bringing two metals in contact with each other, at a short distance from the limb. 4. Only those muscles to which the nerves lead suffer contraction from the Galvanic influence. 5. When a contraction has taken place in any muscle, no other will follow while the metals remain in contact.—In order to renew the motions, therefore, the metals must be separated and joined again. 6. Galvanic excitement, instead of destroying the irritability of a muscle, gives it an additional support. Dr. Valli, an Italian physician, has fully confirmed this principle by the following experiment. “Having prepared the wing of a fowl, or the paw of a cat or dog, I subjected it to the customary trial. At the expiration of half an hour, I armed the other wing of the fowl, or the other paw of the cat or dog, and had recourse to my exciting arc.—The latter wing or paw, however, did not give any sign of electricity, (for he conceived the motion to be occasioned by electricity,) while the parts which had been subjected in the first instance to the experiment, still continued in a convulsed and agitated state.” 7. Galvanic experiments do not succeed so well in a room crowded with persons, as when only two or three individuals are present. 8. Galvanic contractions are more powerful the instant the animal is deprived of life, than some time after; and therefore more violent agitations can be produced in the living animal. 9. Volta concluded that Galvanism was generated by the metal, and not by the animal upon which he operated. These are the principal remarks which we think worth noticing. If they do not content the reader, we must refer him to Wilkinson on Galvanism; where he will find a detail of almost every thing that happened in the Galvanic world till the time he wrote. CHAP. V. _Various Experiments with the Galvanic Pile._ The first experiments which we shall mention were performed by Mr. Cruickshank, with the Galvanic pile. He employed plates of zinc and silver, 1.6 inches square, and the number of plates of both metals varied from forty to a hundred, according to the power required. The lower end of the pile we shall denominate the _silver_ end, because the plate at the bottom is of silver, and the upper end the _zinc_ end, because the uppermost plate is of zinc. The first experiment of Mr. Cruickshank with the Galvanic pile, was upon water and silver wires. These wires were passed through corks, fitted into a glass tube filled with water, and projected about one third of the way, on both sides, into the tube; so that the space between the inner ends of the wires was one third of the length of the tube. One of the corks was made perfectly tight by cement. The tube was then placed upright in a tumbler of water, with the uncemented end downwards.