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,