fo extract the mucilaginous parts of 
c may be applied to vegetables to extract those principles 
soluble in water. It dissolves entirely their essential 
or, and resin ; and as these are often the parts on which 
of vegetables depend, these solutions, or tinctures as they 
re ter are often active preparations. ==. ss 
Equal parts of alcohol and water, in general, extract still more | 
the active matter of plants, as we thus obtain a solution 
e substances which are separately soluble in either of 
oa 
_ When by the action of one or both of these fluids, we obtain a so- 
lution of the active principles of a vegetable, the solution may be 
evaporated to the consistence of a thick tenacious mass. This forms 
what is termed an extract: it is termed an aqueous extract, when ob- 
tained from an aqueous infusion or decoction of a plant, and spirit- 
ous when alcohol has been the solvent. . The design of this prepa- 
on is to obtain the active matter of the vegetable, in a small bulk, 
ind in such a state that it may be preserved a long time without suf- 
fering any alteration. It is evident, that it is a process which can | 
be properly applied to such plants only ashave their virtues dependent 
--on some of their fixed principles, and eyen these are often injured 
by the heat employed, and the free access of the atmospheric air. 
~ Distillation is another process applied to vegetable substances, by 
_ Which we obtain some of. their active principles, “particularly their 
essential oil. Ifthe vegetable matter be heated along with the water, 
_ the oil is volatized, along with the aqueous vapor : it separates from 
_ the water on being allowed to remain at rest ; a part of it, however, — 
is also dissolved, and communicates to the water a considerable de- 
flavor, and often also of pungency. This forms what are 
istilled waters. If alcohol be used instead of water, the es~ 
mpletely dissolved in it, and we thus obtain what are 
' By such processes we extract the active matter of vegetables fi 
: the inert. matter with which it is more or less mixed, snd are eaabtod 
to administer many remedies under a-variety of forms, suited to par- 
ticular circumstances. A-single example will show the utility of in- 
‘Yestigations of this kind, respecting the component principles of 
_ vegetable products, and their relations to the more important chemi« 
ents. Peruvian bark is. one of the most important remedies in 
ul teri medica. Pr: rs have not always found it practi- . 
= exhibit it = with ora as where the stomach 
is uncommo writable, or where, from the nature of the disease, i 
is necessary to give it in large doses, frequently repeated, ne one 
' @¢easion sickness and other uneasy sensations, and even to be re= 
jected by vomiting. Such inconveniences are attempted to be obs 
viated, by giving it in the different forms of infusion, decoction, 
uncture or extract, as any of these may best agree with the patient, 
Our knowledge of its constituent parts ame lead us to the pro- 
per application of these processes. From an accurate analysis of it, 
it has been proved that seven parts out of eight of it, consist ¢ 
woody fibre, or of a matter inert and insoluble, which cannot act Oh 
