INTRODUCTION. 
. 
Marerra Meprea, is that department of the Science of Medicine 
which relates to the knowledge of remedies, or of the effects 
ced in the human system by such substances as are employed 
removal of disease. The objects to be attended to in its : 
-the natural history, the chemical composition and properties, and — 
the medical powers and applications of the substances which belong — 
to it: = es SS | 
The naTURAL History of these substances is of utility in furn 
_ing appropriate characters by which they may be distingt 
Many of them bear a close resemblance to each other, and can on! 
be discriminated by those minute and accurate distinctions which 
the methods of natural history afford. 
From the intimate connexion which freqnently subsists between 
those properties on which natural classification is established, and 
thé various qualities with which bodies are endowed, natural history 
is likewise, to a certain extent, capable of affording indications of = 
the virtues of remedies. Thus, in the vegetable kingdom, the dif 
ferent species of the same genus, and even the different genera of 
the same natural order, are composed of substances which frequent- 
ly exert the same actions on the living system ; yet to this connexion 
there are exceptions so numerous and important, that it is inca- 
pable of just application to any considerable extent: it can only sug- 
gest conjectures which require to be brought to the test of experi- 
ment. ; . 
_. The more full description of the sensible properties of the articles __ : 
of the materia medica affords the most obvious method of distin- 
guishing them, and in many cases the easiest and most certain eri- 
“terion of their purity and perfection. 
* “It has likewise been imagined that the sensible qualities of medi-_ 
‘ines afford indications of their peculiar powers. ‘Those, for ex 
ch are inodorous and insipid, are seldom active ren 
and those which have a similarity | flavor, 
vy 
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