590 
REVIEW OF MOIROUD’S 
Tonics augment the energy of the vital powers, without pro¬ 
ducing any appreciable physical change; while astringents, by a 
kind of chemical action, modify the structure of the tissues, with¬ 
out really augmenting their vital powers. 
This mode of action is particularly evident in the vegetable 
astringents, on account of the tannin and gallic acid which they 
contain combining with the gelatine that prevails in most of 
the tissues. 
The mineral astringents have a more prompt but less durable 
action. Their first impression, always more or less painful when 
applied to a mucous membrane or denuded part, is announced by 
the contraction of the capillary vessels, and the arrest of the flow 
of blood, and the discolouration of the tissue; but when the ap¬ 
plication of the drug has ceased, the vessels regain, by degrees, 
their natural calibre; they are filled again with blood, and even 
carry a greater quantity than before. 
It follows from this, that the topical means which we employ to 
diminish the heat of a part, or to arrest the current of any fluid, 
can only lead to a satisfactory result by being perseveringly ad¬ 
ministered. 
From the power which they are known to have in causing cer¬ 
tain fluids that have been effused in the tissues to enter again into 
the circulation, and also to oppose the inflammation and swelling 
that external violence is calculated to produce, some of the astrin¬ 
gents have been called repercussives or discutients. 
Internally administered, they diminish the internal secretions, 
and render the frncal discharges of greater consistence, and more 
rare and coloured. In this relation they have been confounded 
with tonics; but their action, more circumscribed than that of the 
tonics, is confined to the digestive apparatus alone, unless they 
are given in excessive doses, and too long continued, when they 
may produce considerable derangement. 
The pure astringents are much less employed internally than 
the tonics. They are indicated in chronic diarrhoea, and some 
passive haemorrhages; but they would be injurious in all recent in¬ 
flammations, and in all old ones accompanied by fever, or pain, or 
material alteration of the tissues. 
Some astringents, combined with tonics, acquire an antiseptic 
property, and are beneficial in gangrenous affections. Cinchona 
unites in its composition the active principle of the astringent 
with the bitter one of the tonic. If the pure astringents are not 
often employed internally, their external application is much 
greater. They are used under the form of baths, lotions, fomen¬ 
tations, injections, collyria, and sometimes in the state of powder 
to cleanse unhealthy ulcers; also to suppress chronic discharges 
