different magnets repel each other, and the negative poles repel each other; while positive and negative poles attract each other. The same law of polarization rules in electric or magnetic currents as in magnets at rest.

THE ELECTRIC CIRCUIT.

The Electric Circuit is made up of any thing and every thing which serves to conduct the electric current in its passage—outward and returning—from where it leaves the inner surfaces of the zinc plates in the battery cell to where it comes back again to the outer surfaces of the same plates. When the conducting-cords are not attached to the machine, or when the communication between the cords is not complete, if the machine be running, the circuit is then composed of the battery fluid, the platina plate, the posts, the connecting-wires, which unite the battery with the helix, the helical wires, and their appendages for the vibrating action. But when a patient is under treatment, the conducting-cords, the electrodes, and so much of the patient's person as is traversed by the current while passing from the positive electrode through to the negative electrode, are also included in the whole circuit. And whatever elements may serve to conduct the current in any part of its circuit—be they metal, fluid, nerve, muscle, or bone—the same are all, for the time, component parts of one complete magnet, which, in all its parts, is subject to the law of polarization, precisely as if it were one magnetized bar of steel. Usually, however, it is sufficient for practical purposes to contemplate the circuit as consisting only of that which the current passes through in going from the point where it leaves the positive post and enters into the negative cord, around to the point where it leaves the positive cord and enters into the negative post.

POLARIZATION OF THE CIRCUIT.

I have said, in effect, a little above, that, while the current is running, the entire circuit is one complete magnet, which extends from the inner or positive sides of the zinc plates, where the current commences, all the way around to the outer or negative aides of the zinc plates, to which it returns. Viewed in this light its negative pole or end is the battery fluid, next to the positive surfaces of the zinc plates, and its positive pole or end is the brass clamp which, holding the metals together, is in contact with the outer and negative surfaces of the zincs.

But, for practical purposes, it is sufficiently exact to consider the magnetic circuit as extending only from the positive post around through the conducting cords, the electrodes and the person of the patient to the negative post. The negative end or pole of this magnet is the wire end of the cord placed in the positive post, and the positive end or pole is the wire end of the cord placed in the negative post.

But any magnet may be viewed either as one whole, or be conceived as composed of a succession of shorter magnets placed end to end. If we view it as one entire magnet, we call the end in which the magnetic essence is in greatest quantity the positive end, and the end where it is in least quantity the negative end. But if we imagine the one whole magnet as being divided up into several sections, then we conceive of each section as a distinct magnet, having its own positive and negative poles. And, all the way through, these sectional magnets will be arranged with the positive pole of the one joined to the negative pole of the next in advance of it.

It is just so in respect to the magnetic circuit of a moving current. The whole circuit, as before remarked, is in reality one long magnet. But in applying the terms positive and negative in our practice we often view the whole circuit—the one long magnet—as composed of a series of shorter ones, arranged with positive and negative ends in contact; and all the way the current in each section is supposed to be running from the positive pole of the magnet behind to the negative pole of the magnet before.

We consider the circuit, from the positive post around to the negative post, as composed of three magnets, as follows: Magnet No. 1, which extends from the positive post, along the cord and electrode, to the body of the patient, where the positive electrode is placed. The negative pole of this magnet is the wire end of the cord placed in the positive post, and its positive pole in the positive electrode placed upon the person of the patient. No. 2, which is composed of the parts of the patient traversed by the current between the two electrodes. Its negative end or pole is the part in contact with the positive pole of magnet No. 1, and its positive pole is the part in contact with the negative pole of magnet No. 3. No. 3 extends from the positive pole of No. 2, through the electrode and along the cord, to the negative post. Its negative pole is the negative electrode in contact with the positive end or pole of magnet No. 2, and its positive pole is the wire end of the cord in the negative post.

Since in every magnet the magnetic fluid is supposed to be regularly graduated from minimum quantity in the negative end to maximum quantity in the positive end, this is true in respect to the one magnet, consisting of the whole magnetic circuit, as well as in respect to each one of the sectional series. Consequently there must be the same quantity of magnetism in each negative pole of the sections as there is in the positive pole of the section immediately behind it. And the magnetism of the whole circuit between the positive and the negative posts is in its least volume next to the positive post, and in fullest volume next to the negative post. If we consider the circuit as divided into two equal halves, the negative half is plainly that which joins the positive post, and the positive half that which joins the negative post.

From this it will be seen that what in practice are designated as the positive and negative posts, and also positive and negative poles or electrodes are not such in relation to each other, but the reverse of it; that is to say, the positive post is not positive in relation to the negative post, but is negative to it; and the positive electrode or pole is not positive in relation to the negative electrode, but negative to it. The positive post, like the positive electrode, is called positive, because it is the positive end of the sectional magnet next behind it. And the negative post, as also the negative electrode, is called negative because it is the negative end of the sectional magnet next in advance of it.

THE CENTRAL POINT OF THE CIRCUIT.

The central point of the circuit—that point which divides between its positive and negative halves—is reckoned, in practice, to be the midway point in the line over which the current passes, in its whole course from the positive post around to the negative post. When the cords are of equal length, this point will always be in the person of the patient, about midway between the parts where the two electrodes are applied. This central point, or "point of centrality," is practically neuter—neither positive nor negative; and upon the two opposite halves of the circuit, the positive and negative qualities of the current are in greatest force nearest to the posts, and in least force nearest to the central point. At this point they cease altogether, and the