Chapter I: MADE the same Experiment on those Frogs in which I had, six weeks

before, cut out, from behind, all that part of their Spinal Marrow which is covered by the six undermost Vertebræ, and found, several days after the Frogs had been subjected to the Experiment, that, by pinching their Sciatic and Femoral Nerves, and still more readily by the application of the Gold and Zinc, weak convulsions of the Muscles were excited.

25. AFTER Frogs were prepared as above described, by cutting their Spines transversely, and then all the parts of their Pelves, except their Sciatic Nerves, I found that slight Electrical Shocks, or a Leyden Phial discharged directly through the Limbs of a Frog, or indirectly by the medium of water, produced convulsions in their Muscles, exactly resembling those excited by the Metals. And when, after moderate Electrical Shocks had been passed repeatedly through their Legs, the Metals were applied to their Nerves, in the manner before mentioned, the Muscles were convulsed. I found, likewise, that after cutting the Nerves transversely, and tying them together, Electrical Shocks were conducted by the Nerves, and occasioned convulsions of the Muscles.

WHEN I had killed Frogs, by discharging through them, from their foreheads to their hind feet, large Leyden Phials highly charged, I found their Nerves or Muscles, or both, so much deranged, that feeble convulsions only could be excited by pinching the Nerves, or by applying the Metals to them.

SUMMARY OF FACTS PROVED BY THE FOREGOING EXPERIMENTS.

ON reviewing the foregoing Experiments, we shall find the following Facts fully proved.

1. ON forming a Circle by means of the parts of a living Animal and of two different metallic Bodies, especially Gold and Zinc, in contact with each other, if a Nerve makes part of the Circle, the Muscles in which the Nerve terminates are convulsed.

2. ALTHOUGH the Nerve making part of such a Circle has been cut transversely, yet, if the divided parts of the Nerve are laid in contact with each other, or tied together, the Muscles, in which it naturally terminates, are convulsed.

3. IF the Metals, composing parts of the Circle, are kept steadily in contact with each other, the convulsions of the Muscles cease. But, if they are separated from each other and again rejoined, the convulsions are repeated.

4. THE effects are the same, although the dead parts of an Animal or pure water make parts of the Circle.

5. ALTHOUGH the dead parts of an Animal, making part of such a Circle, are in contact with the Metals, the effects are the same.

6. A MUSCLE making part of such a Circle may be convulsed whilst the matter put in motion is passing in the direction from the Muscle to the Nerve.

7. THE Muscle may be convulsed although it makes no part of the Circle in which the matter put in motion passes, as appears from comparing Experiment 5th with Experiments 13th and 14th. From Experiment 13th, it appears, that the Fluid put in Motion by the Metals passes readily along a Nerve, after it has been cut, providing the divided Parts of it are brought into contact with each other. Yet in Experiment 14th, in which the left hand of the Operator was not applied to the Foot of the Frog, the Muscles in which the Nerve, lower than the Ligature, terminated, were not convulsed, because the Fluid put in motion did not descend lower than the place at which the gold Probe touched the Nerve above the Ligature. We may therefore presume that when a Nerve which has not been cut, as in Experiment 5th, is touched with the gold Probe, the Fluid put in motion does not pass lower in the Nerve than the place of the Probe. Hence we perceive the error of those who suppose that the moisture on the surface of the Nerve conduces the Fluid put in motion to the Muscles, and that their action is in consequence of the direct operation of this Fluid upon their Fibres.

8. THE effects are the same when the Animal and the Metals are insulated, by being placed on Glass, whilst Sealing-wax is interposed between the hand of the Operator and the Metals.

9. IF any part of the Circle is composed of Sealing-wax or Glass, the Muscles are not convulsed.

10. CONVULSIONS are not excited unless the Metals are in contact with each other; and unless both Metals are also in contact with the Animal Substances or the Water making part of the Circle.

RESEMBLANCE OF THE FLUID PUT IN MOTION BY THE FOREGOING EXPERIMENTS TO THE ELECTRICAL FLUID.

THE Fluid set in motion by the application of the Metals to each other, and to Animal Bodies or to Water, agrees with or resembles the Electrical Fluid in the following respects.

LIKE the Electrical Fluid, it communicates the sense of pungency to the Tongue.

LIKE the Electrical Fluid, it is conveyed readily by Water, Blood, the Bodies of Animals, the Metals; and is arrested in its course by Glass, Sealing-Wax, _&c._

IT passes, with similar rapidity, through the Bodies of Animals.

LIKE the Electrical Fluid, it excites the activity of the Vessels of a living Animal, as the Pain it gives and Hemorrhagy it produces seem to prove. Hence perhaps it might be employed with advantage in Amenorrhoea.

IT excites Convulsions of the Muscles in the same manner, and with the same effects as Electricity.

WHEN the Metals and Animal are kept steadily in contact with each other, the Convulsions cease, or an Equilibrium seems to be produced, as after discharging a Leyden Phial.

THE NERVOUS FLUID OR ENERGY NOT THE SAME WITH THE ELECTRICAL NOR WITH THE FLUID PUT IN MOTION BY THE FOREGOING EXPERIMENTS.

THAT the Nervous Fluid is the same with the Electrical, or with the Fluid which is put in motion by the foregoing Experiments, is, I apprehend, disproved by the following circumstances.

1. WITHOUT stating the difficulty there is in conceiving how the Electrical Fluid can be accumulated by or confined within our Nervous System, we may observe that where the Electrical Fluid, or Fluid resembling that put in motion by the foregoing Experiments, is accumulated by an Animal, such as the Torpedo or Gymnotus, a proper apparatus is given to the Animal, by means of which it is enabled to collect and to discharge this Fluid.

2. THE Nervous Power is excited by chemical or by mechanical Stimuli; and, on the other hand, is destroyed by Opium and other Poisons, which cannot be imagined to act on the Electrical Fluid.

3. I HAVE, I apprehend, refuted the theory of Doctors GALVANI, VALLI and others, which supposes that the Nerve is electrified _plus_ and the Muscle _minus_, resembling the Leyden Phial, by shewing that the Muscles are convulsed where there is no communication between them and the Metals, but by the medium of the Nerve; or when the Metals are applied to different parts of the Nerve alone, without touching the Muscles which are convulsed, and when the Muscle which is convulsed makes no part of the Circle in which the Matter that is put in motion passes.

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.

[13] After reading to the Royal Society, on the 3d of June, an account of this Experiment, which I had made in the beginning of May, I found, from an ingenious publication of my Pupil Dr FOWLER, which I received that evening, that the same Experiment had been performed by him.

TRANSCRIBER'S NOTE:

--Obvious print and punctuation errors were corrected.