out by scattering some iron filings on a piece of paper held over the magnet thus made by the current. Thus we can prove the development of

a force in these bars of iron under the influence of electricity, albeit none of that agent entered the bars. But this is not all; the magnetism thus excited by electricity can, in its turn, reexcite that agent. There is no difficulty in proving this in a most unequivocal manner. Thus I will excite magnetism in the bars before me, connect the poles with a bar of soft iron, and turn off the electric current. The magnetism will be in part retained as long as the poles are thus connected; but the moment I slide off the armature the magnetism vanishes, almost all polarity having disappeared. Now, during the restoration of this magnetic equilibrium and the return of the bars to their passive condition, a contemporaneous disturbance of the electric equilibrium of the convolutions of wire wound on the iron bars occurs.

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will now render the bars magnetic, connect the poles with the armature, break the battery connections, and place the terminal wires of the coil surrounding the bars in connection with the large galvanometer at the other end of the table. The needle is now at rest. By sliding the armature off the poles, I destroy the magnetism, and in an instant the galvanometer needle moves on its axis through an arc of 90°, demonstrating the truth of the assertion I made. Thus, then, an electric current excites magnetic force, and a magnetic current in its turn excites electricity.

Let us, then, see what light analogy can throw on the connection of electricity with the nervous influences; and I would ask, May not one of the uses of the electricity so freely developed in the body, especially that existing in the muscles, be to excite in the nervous cords the vis nervosa, just as currents, if passing near a bar of iron at right angles to its axis, excite magnetism? May not this vis nervosa, or nervous polarity, excite the contraction of a muscle without actual contact with its fibres (for we know that the fibrilla of nerves lie· upon, but do not communicate with, the ultimate fibres of muscle), just as the invisible lines of force emanating from the bars of a magnet act upon the suspended bundles of wire or iron filings? Lastly, may not such nervous force again induce electric currents in any glandular or other organs, just as

magnetism in motion will re-excite electricity? thus accounting for what cannot be questioned, the existence of electric currents in certain organs, exclusively excited by, or depending for their existence upon, the integrity of the nervous influence of the part.

I feel that all this is mere hypothesis, but I think it a plausible and probable one; and believing that the vis nervosa is not electricity, although developed under its influence, I suggest it on the strong grounds of analogy, with a firm expectation that the time will come when some such view will be shown to be correct. *

* Since this Lecture was delivered at the College, Professor Matteucci has laid before the Royal Society some further observations, in which he has arrived at conclusions strongly corroborative of the statement I then ventured to make. He says:

"We have thus every reason to conclude that the electric organ of the torpedo, and of all the electric fishes, composed of a great number of elementary organs, and that the elementary organ is nothing else but a nervous fibril in contact with a small cell filled with albumen. And since this cell gives an electric shock when it is subjected to nervous action, we are compelled to admit, that under nervous influence the two opposite electricities separate to be instantaneously re-united. This relation between nervous influence and electricity is, without doubt, of the same nature as that which exists between heat and electricity, between the electric current and magnetism. It is in studying the production of electricity in the different electric fishes, together with the distribution of nervous filaments in their electric organs, that we arrive at a better understanding of this relation between nervous force and electricity. Thus we see in the torpedo and gymnotus the two electric fishes best known physically and anatomically -that the nervous filament always ramifies in the electric organs of these fishes perpendicularly to the axis of the prisms of these organs. Besides which, we know that the extremities or poles of the electric organs in these two fishes are situated at the ex

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I cannot help regarding the phenomenon of what Matteucci has termed "induced contractions," as corroborative at least of the opinion thus advanced. I have said that these manifestations of force we term magnetism and electricity, although not identical as forces, nevertheless mutually excite each other: now, something of this kind has been made out by Matteucci in the case of muscular contractions. This philosopher allows the nerve of his frog-galvanoscope (fig. 9.) to lie across the naked muscles of a frog's thigh: on passing a feeble current of elec tricity through the latter, convulsions occur, not only where they would be looked for, in the leg traversed by the electricity, but where they would not be expected, in the leg whose nerve reposed on the electrified thigh. Now, this could not have arisen from any electricity running down the nerve to the leg; for the very same result occurs when a thin piece of mica or a layer of turpen

tremities of the prisms; in effect, in the torpedo these poles are the ventral and dorsal surface, while in the gymnotus the poles are at the head and tail of the animal.

"It will be seen from this, that in this action of the nervous force, as exercised in the electric organs of these fishes, it follows the same law in developing electricity as does the electric current upon magnetic bodies. In effect, each prism of these electric organs cannot be considered otherwise than as a pile of elementary organs, upon each of which a nervous filament is spread normally to the axis of this pile. Now, a cylinder of cast iron enclosed in a helix of metallic wire, and traversed by the electric current, is evidently an apparatus analogous to a prism of the electric organs of the fish, at the moment when the nervous influence excites the discharge."

tine, both non-conducting bodies, is placed between the nerve and the thigh of the electrified frog. (Phil. Trans. 1847, p. 231.) Nay, it is by no means necessary to apply electricity at all; for if the muscles are made to contract by irritating the spinal marrow of the frog, or even of a rabbit or dog, the claw of the galvanoscopic frog becomes convulsed. With true philosophic caution, Matteucci hesitates to regard this curious discovery as absolutely demonstrative of the evolution of electricity in the act of muscular contraction; and I may adduce it in evidence of the existence of a power exciting nervous force, or something analogous, under similar circumstances to those in which electricity developes magnetism.

Let me now say one word regarding the last of the host of valuable contributions made by our illustrious countryman, Dr. Faraday, to experimental science. He has shown that this excited power, this effect of electricity, this magnetism, is an agent of far more universal sway than was ever previously guessed at. The lines of force emanating from the poles of a magnet are potent in their effects upon all forms of matters. Some metals, as iron, nickel, cobalt, and paper, cork, and even glass, among other bodies, obey the direct attraction of the poles, and, if free to move, arrange themselves in the direction of these lines of force, and take