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REMEDIAL AGENTS. 81

nitric, muriatic and oxalic acids, are examples of the mineral
tonics.
ASTRINGENTS.
Astringents are medicinal agents which produce contraction of
the tissues, having a corrugating power, either directly exerted on
a part, or extended by sympathetic action, and thus removing
morbid affections arising from a state of relaxation, such as in-
flammation of superficial parts, hemorrhage and excessive dis-
charges from mucous membranes. This class of remedies is
irnportant in dental practice, owing to their great efficacy as an-
tiphlogistics. Astringents are divided into vegetable and rnineral^
the former owing their peculiar property of astringency to the
presence of tannic acid, while the latter possess a more decided
astringency, and exert a sedative action on the vascular system.
In the treatment of affections of the mucous membrane, such as
stomatitis^ the object is to arrest the inflammatory action, which
is accomplished by the power of the astringent remedies em-
ployed locally to increase the tonicity of the tissue, and to dimin-
ish the calibre of the vessels supplying the part with blood, thus
diminishing the quantity required for the production of the mor-
bid action. Besides diminishing the current of the blood to the
inflamed part, astringents also exert an influence on the pores or
ducts through which the discharge is poured out, by diminishing
their calibre. Astringents also exert an influence on mor-
bidly relaxed tissues, when such a condition results as the sequelae
of disease, especially in lymphatic temperaments, where flabbiness
of the soft tissues is characteristic.
Care, however, is necessary in the use of astringents, for when
long or immoderately used they may act as direct irritants, in-
ducing inflammation followed by ulceration and sloughing. They
are contraindicated for the arrest of evacuations that are desig-
nated by nature to relieve a plethoric state of the system, unless
such evacuations exist to an alarming extent. This class of
remedies can be readily detected bv the taste, as they convey a
sense of roughness to the palate which cannot be mistaken, and
which is more marked in some substances than in others. Such
agents as tannic acid, gallic acid, nutgall, matico, kino, catechu,
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