I 
INTRODUCTORY LECTURE. 247 
from their solutions by evaporation ; the distillation of liquids 
and the precipitation, fusion, sublimation, etc., etc., of sub- 
stances. Weights and measures, specific gravity, and a nice ap- 
preciation of quantities in general, are important features, and 
are constantly recurred to. 
The relations that vegetable drugs bear to different menstrua, 
and the nature of the matter they cede to these liquids, 
together with the influences that light, heat, and air exercise 
on the solutions, by age or evaporation, constitutes one of the 
chief branches of the subject, including the preparation and 
characteristics of infusions, decoctions, tinctures, wines, syrups, 
extracts^ etc.; in fact the greater part of those vegetable and 
animal preparations which have a complex, inexact composi- 
tion, from the nature of their ingredients. 
To prepare these medicines with judgment, an acquaintance 
with the proximate constituents of drugs is essential, those that 
are active ascertained, and the modes of treatment most adapted 
to their removal applied. For instance, Krameria contains a pe- 
culiar tannin, apothegm, starch, and coloring matter amongst its 
ingredients ; the tannin being active and the rest inert, — and it is 
desirable to prepare an extract which shall possess the greatest 
possible activity. Now it has been ascertained that apothegm 
and starch are insoluble in cold water, but are dissolved by it 
when boiling, after which the starch and a part of the tannin 
combine to forma compound insoluble in cold water. Alcohol 
dissolves the tannin and apothegm and not the starch. Hence 
it must be apparent at a glance that the extract prepared with 
cold water must be superior to any other, inasmuch as it con- 
tains neither apothegm nor starch. 
Again : — In the preparation of the oil of bitter almonds or 
bitter almond water, experience has proved that when the 
ground kernels are allowed to macerate in cold water for 
twenty-four hours before the distillation is commenced, the 
product is larger, if the oil, and stronger if the water is in 
question ; a result very natural, when the properties of the con- 
stituents are understood. These kernels contain amygdalin 
