_Violent Exercise_—_Ammonia_—_Guaiacum_—_Alcohol_—_Warm Bath_.
III. BY RELAXING THE MORBIDLY CONSTRICTED MOUTHS OF THE PERSPIRATORY
VESSELS.
_Antimonials_—_Cold Affusion_—_Venesection_—_Saline
Diaphoretics_.
The action of the cutaneous vessels may be augmented by heat, without
necessarily increasing, at the same time, that of the heart and
arteries; hence it is that heat is, of itself, often sufficient to
produce sweating, while it generally accelerates the operation of a
sudorific medicine. To this general proposition, however, there are some
very important exceptions; and, indeed, in certain conditions of the
cutaneous surface, the stimulus of heat will be even found to impede,
rather than to promote, diaphoresis; thus in the hot stage of a
continued fever, there would seem to exist a peculiar constriction of
the perspiratory vessels, accompanied with extreme heat and dryness. In
such a state, remedies of the third class must be applied, or conjoined
with those of the former. The warm bath may be said to partake of _all_
the qualities upon which our classification is founded; it will
stimulate the cutaneous capillaries,—increase vascular action,
generally, and, by its emollient powers, relax the morbidly constricted
mouths of the perspiratory vessels. During the ardent heat of fever, the
external application of cold is the most efficient sudorific, as the
valuable reports of Dr. Currie have very satisfactorily established.
Although the _external_ application of cold was not often employed in
the hot stage of fever, until within the last thirty years, yet the
administration of cold _drinks_ appears to have been practised by the
ancients, as an expedient to produce perspiration. Galen, and his
immediate disciples, as well as the physicians of the sixteenth century,
seem to have frequently administered cold water for the purpose of
exciting sweat in fevers.[162] Celsus also describes the beneficial
effects which arise from copious draughts of cold water in ardent
fevers, “fereque post longam sitim et vigiliam, post multam satietatem,
post infractum calorem, plenus somnus venit, per quem _ingens sudor
effunditur_, idque præsentissimum auxilium est.”[163] Cold water, when
introduced into the stomach in the hot stage of fever, must produce its
diaphoretic effect through the sympathetic relation which subsists
between that organ and the skin. Nauseating doses of _Antimony_, and of
other emetics, occasion a relaxation of the surface from the same mode
of operation, and in this latter case, if the force of the circulation
be at the same time increased by tepid diluents, the diaphoretic effect
is more certain and considerable.
_Alcohol_, _Guaiacum_, and other powerful stimulants, produce their
effects by merely accelerating the circulation; but in employing such
remedies for the purpose of exciting sweat, we must be careful to adapt
them to the circumstances of the case, and to the degree of action which
prevails. In all febrile diseases attended with much increased heat, or
connected with local inflammation, diaphoretics of this description must
be very cautiously administered, for by accelerating the circulation
they might counteract any benefit which they would otherwise confer by
relaxing the vessels of the skin. In the whole history of medical
opinions there is scarcely a theory which has proved so fatal in its
practical applications as that maintained by Van Helmont, and his
disciples, viz. that _acute diseases were to be cured by expelling some
morbific matter, after its proper concoction_—a theory which suggested
the administration of the most stimulating sudorifics, together with
high temperature[164] in every grade of febrile exacerbation. The fatal
effects of such a practice during the seventeenth, and early parts of
the eighteenth centuries, are incalculable, and may be very
satisfactorily contrasted with the beneficial results which have
accrued, in the same diseases, in the present age, from the use of
diaphoretics of the refrigerant kind.
_Saline Diaphoretics_, as they readily pass with the chyle, may be
supposed to enter the circulation, and be thus brought to act, directly,
on the cutaneous vessels; at the same time it seems extremely probable
that such remedies may also occasion an impression on the stomach, which
is sympathetically communicated to the vessels of the skin; they have
undoubtedly little or no influence on the general vascular system, and
neither augment the force nor the velocity of the circulating current.
It is not, however, in febrile affections alone that this class of
remedies proves highly beneficial; the very intimate sympathetic
connection which subsists between the functions of the lungs and skins,
renders the use of such medicines particularly advantageous in the cure
of the diseases incident to the former of these organs; a fact upon
which we shall hereafter offer some remarks under the history of
_Expectorants_.
So again, in the treatment of bowel affections, in consequence of the
intimate relation which exists between the cutaneous capillaries and
those of the internal organs, gentle diaphoretics offer a valuable
resource in their cure. How frequently do Diarrhæa, Enteritis, &c. ensue
from the sudden suppression of perspiration by cold?
From the influence which these medicines exert upon the extreme vessels
of the skin, they are also highly serviceable in various obstinate
cutaneous affections, as _Herpes_, _Lepra_, &c.
As evacuating the serous part of the blood must necessarily have an
indirect effect in promoting absorption, _Sudorifics_ have been
occasionally exhibited in Dropsy, especially in that form of the disease
called _Anasarca_. It has been already observed that cases too
frequently occur in which the discharge of urine cannot be increased by
art; upon such occasions practitioners have sometimes had recourse to a
trial of Sudorifics,[165] but from the great difficulty which generally
exists in exciting sweating in such affections, the indication has
rarely been fulfilled. Where however a sudorific does succeed, it is
less liable to debilitate than the other alternative of a drastic
purgative.
There is still another point of view in which the therapeutic importance
of Diaphoretics may be considered. It is generally acknowledged that by
cutaneous transpiration a portion of excrementitious matter is ejected
from the system; hence by the failure or imperfect performance of this
function, a deleterious fluid is retained which may give origin to
disease; to such a cause may perhaps be attributed the generation of
Calculi, and other diseases of the urinary system, as we shall have
occasion to notice under the head of _Lithonthryptics_.
The increased efficacy which these medicines derive from combination
with each other, will form a subject of interesting enquiry in the
succeeding essay.