lysed by mere exposure to heat: sometimes 
the atmospheric air is admitted in conjunc- 
tion with heat; fermentation is often employ- 
ed to separate the constituent principles of 
materials ; lastly, nitric acid is much used 
in analysis, by which oxygen is communi- 
cated to the substance operated upon; and 
by t he resulting compound, the nature of the 
ucidi liable base is indicated. 
Gum is one of the most abundant among 
the proximate principles of vegetables. It is 
glutinous, insipid, without odour, and soluble 
in water, constituting a viscid solution, deno- 
minated mucilage. It is insoluble in alcohol, 
ether, or oil. It does not absorb oxvgen 
from the atmosphere; it is neither volatile 
nor fusible. At a temperature beyond the 
boiling point, but beneath that of ignition, 
gum is decomposed, and affords an impure 
acetous acid, ammonia, carbonic acid, and 
carbonated hydrogen gases ; the residuum is 
charcoal with a certain quantity of lime. 
The ultimate principles of gum are oxygen, 
hydrogen, carbon, azote, and lime. The me- 
dicinal qualities of gum are trivial. In phar- 
macy it is employed principallyias a medium 
of mixture between oils and water. 
Resin. This is another proximate prin- 
ciple existing in abundance in vegetable pro- 
ducts. It is generally, but not always, united 
with gum. Resin is not soluble in water, 
but, unlike gum, is soluble in alcohol, ether, 
and oils. Resin does not absorb oxygen; 
when heated to ignition it burns ; and" is fu- 
sible by a heat nearly that of boiling water. 
W hen volatilized, however, it is invariably 
decomposed: its products are water, acetous 
acid, a burnt oil, and a charcoal residuum. 
Its ultimate principles are carbon, hydrogen, 
and oxygen. 
Resins are much more active on the living 
system than gums. The virtues of many 
medicinal substances depend exclusively on 
their resinous part. 
The extractive matter is another vegetable 
principle, which until lately was confounded 
with the gum and resin. This is equally so- 
luble in water and in alcohol. It likewise, 
at a certain temperature, absorbs oxygen. 
It affords, upon being exposed to heat, em- 
pyreumatic acid and oil, and some ammonia. 
Jts elements are carbon, hydrogen, oxygen, 
and azote. 
This vegetable principle it is difficult to 
obtain pure and unmixed. 
Oil. This is of two kinds, expressed or 
unctuous, and volatile or essential. These 
have some qualities in common, and others 
characteristic of each. Expressed oils are 
viscid, almost without taste or odour: they 
congeal by cold, and are insoluble either in 
water or alcohol. With alkalies they form 
soap. At a temperature of 212°, they are 
decomposed, and afford water and carbonic 
acid. Their ultimate principles are carbon, 
with a small proportion of hydrogen. 
These oils are generally found in the seeds 
and fruits of vegetables, from which they are 
separated by mechanical pressure, or by 
■ boiling. Some of them have medicinal vir- 
tues, but they are commonly employed 
merely as lubricants. 
Volatile or essential oils are quickly dissi- 
pated by the heat of boiling water, without 
suffering decomposition. They are more 
soluble in alcohol than in water. * They slow- 
Vol. 11. 
PHARMACY. 
Iy absorb oxygen, and are at length changed 
into resinous matter. They contain more 
hydrogen than the fixed oils.' 
Essential oil exists in abundance in the 
aromatic plants, and appears to constitute 
their aroma, although some chemists have 
supposed this last to be a peculiar and exclu- 
sive principle. It is usually extracted from 
the vegetable by distillation. As medicines, 
these oils are highly stimulant. The natural 
combination of essential oil and resin, which 
exists in some plants, constitutes balsam, 
which in some cases has also a peculiar acid 
in its composition. 
Camphor. This is a distinct vegetable 
principle. It is insoluble in water, but is so- 
luble in alcohol, oil, and ether. It evapo- 
rates even at the ordinary temperature of the 
atmosphere. When distilled, it is decom- 
posed, and affords a pungent volatile oil, 
amounting to nearly one-third of its weight’ 
while carbonic and hydrocarbon ic acid gases 
escape, and a quantity of charcoal remains. 
Camphor then appears to contain a greater 
proportion of carbon and perhaps of oxygen 
than the essential oils. The medicinal powers 
ot camphor are very considerable. 
Y ax is a solid, tenacious, and inflammable 
principle, holding nearly the same relation to 
expressed, that camphor does to essential, 
oil. 
Eecula is an important principle in vege- 
tables. It is, when existing separately, mild 
and insipid. It is not soluble in cold' water. 
YV ith boiling water, it forms a jelly. Ills in- 
soluble in alcohol. It is converted by cer- 
tain processes into sugar. Eecu'a is com- 
posed of oxygen, carbon, and hydrogen. It 
is by far the most nutritious piincipie in ve- 
getables. 
Gluten. A thick fibrous substance found 
in the farina of some plants. _ It is insipid, 
elastic, insoluble in water, and but sparingly 
soluble in alcohol. Its prominent principle 
appears to be azote. 
Albumen, like gluten, is named from its 
resemblance toa principle in animal matter. 
This is soluble in cold water, and coagulated 
by heat or alcohol. It affords much ammo- 
nia on exposure tx> heat. 
Saccharine matter is generally found united 
with gum and extract. It is soluble in water, 
and in alcohol. It is converted by fermen- 
tation into alcohol ; and this last, ‘by a se- 
cond “stage ot fermentation, becomes acetous 
acid. Saccharine matter consists of oxygen, 
carbon, and hydrogen. 
The saline principle in vegetables is named 
their essential salt. Essential salts are either 
acids or neutrals. 
r l he native vegetable acids which have 
been detected, are seven, viz. the malic, 
which is contained in apples, and other fruits, 
previous to their maturity. It is converted 
into the oxalic acid by the agency of nitrous 
acid. 
I lie oxalic. This has the largest propor- 
tion of oxygen, of any native vegetable acid. 
It is soluble, and capable of crystallization. 
Its distinguishing property is its very strong 
attraction for lime. 
The citric. This attracts the earths in 
general more forcibly than the alkalies. 
1 he tartarous, which is extremely soluble 
in water, and crystallizable. It has been 
imagined to contain a larger portion of hy- 
drogen than’ any other of the acids, 
3 D 
3.93 
■The acetous. This acid is more usually 
the produce of fermentation. It is however 
toimd native in the sap of the vine, &c. It 
yields upon decomposition a small portion of 
ammonia. 
benzoic acid is found in several balsams 
and gum-resins. This is soluble in boiling 
water, and upon cooling separates in white 
flakes. 
I he gallic is the last of the native vegetable 
acids. 1 his has generally bten supposed to 
constitute the principle of ^stringency in ve- 
getables. It exists abundantly in gall-nuts, 
and other vegetable astringents. Its distin- 
guishing property is its forcible attraction 
to the oxides of irort, with which it forms a 
precipitate of a very deep black. The gallic 
acid contains a large quantity of carbon, with 
some oxygen, and a very small quantity of 
hydrogen. 
i he tannin, or tanning principle, lias bees 
til i lately confounded with the gallic acid., 
i his principle is characterized by its faculty 
ot combining with animal jelly, and forming 
a hard insoluble substance. Tannin is found 
in considerable quantity in vegetable astrin- 
gents, and is usually united with the gallic 
acid. 
besides the above vegetable acids, several 
compounds exist in some vegetables, formed 
by the junction of sulphuric, nitric, muriatic, 
carbonic, and phosphoric acids, with the al- 
kalies and earths. 
r ! he ligneous part, or fibre, of the vege- 
table, is enumerated among its proximate 
principles. ] his is in a manner the basis for 
the attachment of its other principles. It is 
insipid and insoluble. With nitrous ‘acid it 
affords the malic and oxalic acids. It ap- 
pears to be principally formed of carbon, 
combined with oxygen and hydrogen. 
from the above enumeration of the proxi- 
mate principles in vegetables, the utility ot 
those pharmaceutical processes to which thev 
aie subjected, may with facility be perceived. 
These we need not again describe; but shall 
conclude the present section by a general 
notice of the principles of such animal sub- 
stances as are medicinally employed. Thft 
number of articles which are received into the 
materia medica from the animal kingdom is 
comparatively small. Animal have the same 
geneial chemical characters with vegetable 
products. The principal difference is con- 
stituted by the superior disposition of the for- 
mer to undergo the putrefactive process, and 
by their affording a larger quantity of ammonia 
or volatile alkali when- decomposed by heat: 
these peculiarities appear to be principally 
derived, as above noticed," by the presence 
of azote in a much larger proportion in ani- 
mal than in vegetable matter. This in de- 
composition unites with the hydrogen which 
animal substances likewise contain in abund- 
ance, and thus constitutes the ammonia. 
Animal substances contain likewise sulphur 
and phosphorus ; and for the most part the 
carbon which enters into their composition is 
much inferior in quantity to what is found in 
vegetables. 
The vegetable gluten and albumen we 
have already described as resembling the ani- 
mal. Animal fat bears a considerable resem- 
blance to vegetable oil. Gelatine is like mu- 
cilage or fecula. Milk contains a principle 
similai to the saccharine matter in the vege- 
