I have already said that when the conducting-cords are of equal length, as for the most part they should be, the central point of the circuit will be in the person of the patient, about midway between the two electrodes. Now, since the current always runs from the positive to the negative pole, and makes its whole circuit in that direction, it will be readily seen that, from the place on the patient where the positive pole is applied, inward as far as to the central point, the direction of the current may properly be said to be _inward_; and that, from the central point to the place of the negative electrode, where the current comes out, its direction may be said to be _outward_. When, therefore, a part is treated with the positive pole, or when the part under treatment appears anywhere between the positive pole and the central point, it is not unusual to say, It is treated with the _inward current_. And when a part is treated with the negative pole, or when it appears between the central point and the negative pole, it is often spoken of as being treated with the _outward current_. MECHANICAL EFFECT OF EACH POLE. The _mechanical_ effect of the forward end of the current, or that part of it which is under the negative electrode, is to relax, expand and weaken; while that of the rear end, under the positive electrode, is to contract and strengthen. A moving ship disperses the waters at its bow, but draws them in at its stern. The bullet shot from a gun, in passing through a plank, leaves the perforation closed where it enters in, but wide open where it comes out. Thus, in physics, the advance end of a moving body tends to disperse the element through which it is passing, while the rear end tends to its contraction. Analogous to this are the _mechanical_ effects of the different ends of an electrical current in the living tissue. When, therefore, we wish to relax a muscle that is unnaturally contracted, as by rheumatism or otherwise, we must bring it under the forward end--the outward current--the negative pole. If we desire to contract ligaments or muscles that are abnormally relaxed, (not _atrophied_), as in prolapsus uteri, we must subject them to the rear end of the current--the positive pole. Parts that are unnaturally contracted are electrically negative in excess, and need to be made more positive. And parts that are unhealthily relaxed are too positive, and should be made more negative. We make a part more positive by applying to it the negative pole, and more negative by applying to it the positive pole. Parts _spasmodically_ contracted are acute and positive; those _permanently_ contracted are chronic and negative. RELAXED AND ATROPHIED CONDITIONS.