> circulation, arid increase the heat of the body. They are 
_searcely sufficiently permanent in their action to be used by them- 
selves, as tonics ; but.they always promote the action of bitters and 
_ astringents, and are used with advantage to obviate symptoms aris- 
debility of the stomach or intestinal canal. Their aro- - 
ty in general resides in an essential oil, which in each of 
varies in flavor, pungency, and other sensible qualities, but 
ich is nearly alike in its chemical properties. It is soluble en- 
‘in alcohol, is sparingly soluble in water, and is extracted from 
o by distillation. ane eS 
r 
CLASS IV.—ASTRINGENTS. 
Astrincents have been usually considered as substances capable 
_of obviating or removing increased evacuations, by their power of 
_ constringing or condensing the simple solids, of which the vessels 
formed, and this by an action entirely chemical or mechanical, 
that which they exert on dead animal matter. , 
. wing, however, these substances to possess some power of this 
_ kind, their effects as remedies cannot be explained merely from its 
_ exertion. Increased evacuations cannot be ascribed to mere me- 
chanical laxity of the solids ; and their remoyal cannot be referred © 
to simple condensation of these solids. Neither can it be admitted — 
that active substances may be applied to the system without occa- 
sioning changes in the state of the living powers. Many substances, — 
ranged as astringents occasion very considerable alterations in S€- 
veral of the functions; they produce effects too which cannot be — 
solely referred to a condensing power, and therefore in all the 
changes they produce, part at least of their operation must be re- 
‘ferred to their acting on the powers peculiar to life. > gee 
a For reasons of this kind, some have denied the existence of such 
medies, and have considered those which usually receive the ap- 
pellation of astringents, merely as stimulants, moderate and perma- 
nent in their action; in other words, as tonics of inferior powel+ 
But though there be a great analogy between these two classes ! 
their effects, and probably in their mode. of operation, there 1s a8 
avery obvious difference ; the most powerful astringents, that 38, 
substances which immediately restrain excessive evacuations, Del 
much inferior in real tonic power to other substances having 
astringency ; while there are powerful tonics or medicines capable 
3 ‘of removing debility, which do not with any uniformity produce the ; 
- ‘Momediate effects of astringents. ie. 
Perhaps. astringents may be regarded as moderate, pet 
stimulants having their stimulant operation modified by their 
of condensing the animal fibre by a mechanical, or rather 
cal action, That they exert a stimulant operation, is pi 
their power of curing intermittent fever, and other diseases nly 
y ; and that they. possess a constringing quality is evdient, not 0) 
the sensation they excite on the tongue, but is proved by Menges 
change they produce in animal matter, If these combined ac 
be exerted on the fibres of the stomach, the change ] ro 
