_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.