The term _Diaphoretic_ has been applied to those medicines which
increase the natural exhalation of the skin, and when they act so
powerfully as to occasion sweating, they have been commonly
distinguished by the name of _Sudorifics_, but as no difference exists
between these remedies, but in the degree of force with which they act,
we may very properly comprehend the whole under the general title of
Diaphoretics: the fluid effused is also in both cases similar, but in
the one it is discharged more slowly, and is carried off by the
conducting[161] power of the air, in the insensible form of vapour,
while in the other case it is so copiously effused from the exhalant
vessels, as to appear in the liquid form.
As obstructed perspiration may depend upon very different, and even
opposite states of the system, so may the most adverse medicines fall
under the denomination of diaphoretic remedies.
In some affections, a deficient diaphoresis may be associated with
increased vascular action, and in others, with a slow languid
circulation.
Diaphoretics may be considered as operating, either by directly
stimulating the cutaneous capillaries;—by increasing the general action
of the vascular system;—by relaxing the morbidly constricted mouths of
the perspiratory vessels;—or, lastly, by producing at once both the
latter of these effects.
In conformity with the plan adopted on other occasions, I shall proceed
to investigate the powers of this class of medicines, according to their
supposed modes of operation.