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.