4. I HAVE proved, that the Muscles are convulsed whilst the current of the Electrical Matter is passing from them and from the smaller Branches of the Nerves into their Trunks; and as a Muscle is never thrown into Action by the Nervous Energy, except when this passes from the Trunk of the Nerve into its Branches, and from these into the Muscle, it appears that when, in these Experiments, the Muscles were convulsed, the Nervous and the Electrical Fluids were moving in opposite Directions; from which we may infer, that, in their Nature, they differ essentially from each other. 5. THE Nervous Energy is stopped by a tight Ligature or by the transverse Incision of a Nerve, although its divided Parts are thereafter placed in contact with each other; whereas the Electrical Fluid or the Fluid excited by the Metals, passes readily, downwards or upwards, along a Nerve which has been tied or cut. 6. AFTER the Limb of a living Animal has been amputated, frequent Convulsions of the same Muscles may be excited by applying Mechanical or Chemical Stimuli to its Nerves; whereas Electrical Matter discharges itself suddenly. HENCE I conclude, 1. THAT the Fluid, which, on the application of Metalline Bodies to Animals, occasions Convulsions of their Muscles, is electrical, or resembles greatly the Electrical Fluid. 2. THAT this Fluid does not operate directly on the Muscular Fibres, but merely by the Medium of their Nerves. 3. THAT this Fluid and the Nervous Fluid or Energy are not the same, but differ essentially in their Nature. 4. THAT this Fluid acts merely as a Stimulus to the Nervous Fluid or Energy. 5. THAT these Experiments have merely shown a new mode of exciting the Nervous Fluid or Energy, without throwing any farther or direct Light on the nature of this Fluid or Energy. FINIS. FOOTNOTES: [1] See Edin. Phys. Ess. Vol. III. [2] See Edin. Phys. Ess. Vol. III. [3] See Observations on the Nervous System, 1783, Chap. x. and xi. [4] See FONTANA sur les Poisons, 1781, p. 267. [5] See FONTANA, p. 293. [6] FONTANA, p. 244. [7] FONTANA, p. 259. [8] FONTANA, p. 112. p. 259. [9] FONTANA, p. 142. [10] Edin. Phys. Ess. published in 1771, p. 363. [11] Very small portions of different metals, applied as above described, have astonishing effects; and although I have found that large portions of the metals produced convulsions, when smaller had failed, or that they produced stronger convulsions; yet the effects are by no means proportioned to the weight of the metals employed, nor to the extent of their surfaces which are suddenly brought into contact. In most of my Experiments, I employed a plate of Zinc, about five inches long, three inches broad, and about one-third of an inch thick; and a gold Probe, somewhat thicker and longer than the Probes Surgeons commonly use. [12] See Dr FOWLER'S Book, p. 85.