There are three species met with in the shops, viz.
1. ALÖE SPICATA, L. Socotorina, D. Socrotrine Aloes.
PERFOLIATA. E. Cape Aloes.
2. ALÖE VULGARIS.[362] L. Hepatica, E. D. Common or Barbadoes Aloes.
3. ALÖE CABALINA. Fetid, Cabaline, or Horse Employed only by Farriers.
Aloes.
QUALITIES. The above varieties of aloe differ in their purity, and
likewise in their sensible qualities; the _Socotrine_ is the purest, it
is in small pieces of a reddish brown colour; the _Barbadoes_ is in
large masses, of a lighter colour, and having an odour much stronger and
less pleasant; the _Cabaline_ is still more impure and less powerful.
All the kinds are characterized by an intensely bitter taste, which, in
the _Socotrine_, is accompanied by an aromatic flavour. CHEMICAL
COMPOSITION. In this there appears to be some obscurity; M. Braconnot
(_Ann. Chim. tom. 68._) conceives it to be a substance, _sui generis_,
which he terms “_bitter resin_,” while others regard it as composed of
resin, gum, and extractive, the proportions of which are supposed to
vary in the different species, but that their peculiar virtues reside in
the extractive part. SOLUBILITY. It is to the slowness with which aloe
undergoes solution in the _primæ viæ_, that it is indebted for the
medicinal properties which distinguish this substance; by boiling water
it is dissolved, but on cooling a precipitation ensues, and by long
decoction it becomes quite inert; weak acids dissolve it more abundantly
than water, but proof spirit is the most perfect solvent: its solubility
is increased by the addition of alkaline salts and soaps, but by such a
combination it undergoes a material change in its medicinal properties;
the bitterness is diminished, its purgative effects impaired, and it
ceases to operate specifically upon the large intestines, a fact so far
valuable, as it enables us in certain cases to obviate its irritating
action upon the rectum. MEDICINAL USE. Aloe is a bitter stimulating
purgative, emptying the large intestines, without making the stools
thin; it likewise warms the habit, quickens the circulation, and
promotes the uterine and hemorrhoidal fluxes. DOSE, gr. v.–xv. No
greater effect is produced by a large dose than from one comparatively
moderate; its tendency, however, to irritate the rectum renders it, in
many cases, an objectionable remedy;[363] and its sympathetic action on
the uterus may occasionally produce mischief, in irritable habits, while
in other states it may, for reasons equally obvious, prove beneficial.
FORMS OF EXHIBITION. The form of pill should be preferred on account of
its extreme bitterness, as well as being, for the reasons above
mentioned, the one most likely to fulfil the intention of its
exhibition; for in addition to what has been stated in a preceding part
of this work, on the important influence of solubility, it may be here
observed that since the aloe does not undergo solution in the stomach,
it is admirably adapted for the basis of remedies intended to obviate
constitutional costiveness, for in our endeavours to supply the
deficiencies of nature by the resources of art, we should at least
attempt to imitate the modes of her operation; the natural stimulus of
the intestines, the bile, is poured into them below the stomach, and
whenever it regurgitates into that organ it produces disease; so it
happens with our cathartic medicines, and unless we so modify their
solubility that their operation cannot commence until after their
passage through the stomach, we shall find that we only increase the
evil we are endeavouring to obviate, and that, in addition to the torpor
of the intestinal canal, we shall induce the stomach to participate in
the disease, or excite a morbid fretfulness of that organ which will be
attended with the most distressing symptoms.[364] _See Formulæ_ 12, 13,
79, 80, 81. Aloes in combination with assafœtida furnishes an eligible
purgative in the dyspepsia of old persons; it is also well calculated to
obviate the costiveness so generally produced by Opium, (_Form:_ 11, 12,
13.) See also p. 162. OFFICINAL PREPARATIONS. _Pulv: Aloes comp:_ L.
_Pil: Alöes cum Myrrha._ L.E.D. Pil: _Aloes comp: Pil: Alöes cum
Assafœtida._ E. _Pil: Aloes cum Colocynthide._ E. _Pil: Cambogiæ comp:_
(=B.M.=) L. _Pil: Rhei. comp:_ (=F=) E. _Pil. Scammon, cum Aloe._ D.
_Decoctum Aloes comp:_ L. _Extractum Aloes purificatum._ L.D. _Extractum
Colocynthidis comp:_ L.D. (=F=) _Tinct: Alöes_ L.E.D. _Tinct: Alöes
comp:_ L.E.D. Tinct: Alöes Ætherea, E. _Tinct: Benzoin: comp:_ (=G=)
L.E.D. _Tinct: Rhei et Aloes_ E. _Vinum Alöes._ L.E.D. ADULTERATIONS. It
is frequently adulterated with common resin, but the fraud more
generally committed is that of mixing with, or substituting the inferior
species for the Socotrine, but the _Barbadoes Aloes_ may, independent of
its want of aromatic flavour, be distinguished from the Socotrine by a
simple test, for the latter dissolves entirely in boiling water and
alcohol, whereas the former, when treated in a similar manner, leaves a
considerable residue; sometimes the _Horse Aloes_ is made to appear so
bright and pure, as not to be easily distinguished by the eye even from
the _Socotrine_, but its rank odour, of which no art can divest it, will
readily betray the fraud.
ALUMEN. (_Super-sulphas Aluminæ et Potassæ._) Sulphas Aluminæ. E.