There is still another kind of aloes, named Foetid or Cabal-line, but on account of its foetid odour it is not used in medicine. A Mocha aloe resembling the Cape, but less purgative, is also brought to this country.

1 'Aλon Dioscoridis, 1. 3. c, 25.

Qualities.-The odour of the Barbadoes aloes is stronger and less pleasant than that of the Socotrine, and has some resemblance to the odour of the human axilla. The taste is nauseous and intensely bitter. The pieces are also of a duller and deeper brown colour, less glossy, not so smooth in the fracture, but they easily splinter. The edges are not so sharp and transparent; but rather blunt, and of a dull yellowish hue. It softens in the hand, and is adhesive. The colour of the powder is a dull olive yellow. The Barbadoes are chiefly used as horse, medicines.

All the kinds of aloes, when analysed, yield a small portion of vegetable mucus and resin, and a peculiar extractive matter. Braconnot found aloes to consist of 73 per cent. of a peculiar bitter matter, which he has termed the resinous bitter principle1, resino amer; and 26 of a pure coloured principle, principe pure: Bouillon, Lagrange, and Vogel consider that aloes contain both resino-extractive and a resinous principle, in the proportion of 58 of the former and 42 of the latter. The odour, taste, and medical virtues of the drug reside chiefly in the extractive; and the superiority of the Socotrine, the Cape, and the Bombay aloes, is correctly supposed to arise from their containing a larger proportion of it, and consequently less resin, than the Barbadoes. Boiling water dissolves nearly the whole of any of the kinds; but as the solution cools, a portion is deposited; and by boiling aloes in water the extractive is altered, rendered insoluble in water, and approaches in its properties to the nature of resin. The alkalies and their carbonates greatly assist its solution. All the kinds dissolve, also, in proof spirit.

When the Socotrine aloe is distilled, a volatile oil is obtained, which is not procured from the Barbadoes; but Trommsdorff found albumen in this variety, and not in the Socotrine aloes. Pfaff examined the extractive, which he calls Aloesin, and ascertained the following effects of re-agents on it:-It is soluble in water and alcohol, insoluble in ether. It imparts a bluish green colour to litmus paper reddened by an acid. It is deepened in colour by alkalies, rendered paler by acids, and clarified by alum. It is precipitated by protonitrate of mercury and acetate of lead; and scantily by nitrate of silver and nitrate of lead. Persulphate of iron deepens the colour of the solution, but throws down no precipitate. It is not affected by tincture of galls, muriate of tin, tartar emetic, or solutions of the salts of copper, zinc, or manganese. By distilling eight parts of nitric acid on one part of aloes, and washing the residue with water, a

1 Ann. de Chymie, lv. 152, reddish yellow precipitate is formed, which, when washed and dried, falls into a beautiful golden yellow powder. This is the bitter principle of aloes; and, according to the experiments of M. Leibeg, it is a compound of carbazotic acid and a resinous principle. This bitter principle has been supposed to be the active cathartic principle of aloes; but this requires confirmation. It forms a beautiful purple dye.

Medical properties and uses.-Although all these kinds of aloes differ in their sensible qualities, yet they agree in their medical properties. They are warm, stimulating cathartics, of slow solution; they act chiefly on the colon and rectum. By the extension of their stimulus to the uterine vessels, they produce, also, emmenagogue effects. Their operation is slow and moderate, but certain. From the stimulant property of aloes, they are useful in cases where the intestines are in a sluggish, relaxed, and insensible state, attended with viscidity of the abdominal secretions; as in the habitual costiveness of the sedentary and hypochondriacal, or that arising from a paucity of bile, in jaundice, chlorosis, and scrofula: and as the rectum participates in their action on the colon, they have been found very serviceable in expelling ascarides. Their effect upon the rectum is more owing to the manner of prescribing the remedy, than any specific action which it exerts on that portion of the intestines, which is but little affected when the aloes are prescribed in a soluble form. They are generally thought to be improper in very irritable and plethoric constitutions, in phthisis pulmonalis, and during the flow of the menses.

Aloes and aloetic compounds have been likewise regarded as improper in pregnancy; but Dr. Denman has justly remarked, that "they are in common use among the lower class of people, because they are cheap, and conveniently given in the form of pills1;" and no bad effects are observed to follow.

Aloes may be given in substance, in doses from grs. ij. to grs. x., larger doses not operating more effectually. Whether in the simple state, or when compounded with soap, bitters, metallic salts, and other substances, the form of pill is to be preferred, on account of the nauseous taste of the medicine.2

1 Introduction to Midwifery, vol. i. 287.

2 Dr. Paris (see Pharmacologia) has enumerated the following empirical preparations as owing their efficacy chiefly to the aloes they contain. Anderson's pills, consisting of aloes, jalap, and oil of aniseed; Hooper's pills, formed of Pil.

Aloes c. Myrrha, sulphate of iron, and Canella bark; Dixon's antibilious pills, a compound of aloes, scammony, rhubarb, and tartar emetic; Speediman's pills, of aloes, myrrh, rhubarb, the extract and the essential oil of chamomile; and Lady Webster's dinner pills, for which the following is the formula, extracted from the old Paris codex. R. Aloes optima?, 3 vj. mastiches, et rosarum rubrarum, a a 3 ij. syrupi de absinthio qs. ut fiat massa, in pilulas 120 dividenda.

Officinal preparations.-Pulvis Aloes comp. L. D. Pulv. Aloes cum Canella, D. Pilulae Aloeticae, E. Pil. Aloes comp. L. D. Pil. Aloes cum Myrrha, L. E. D. Pilul. Aloes et Assafoetidae, E. D. Pilulae Cambogiae comp. L. E. D. Pil. Aloes cum Colocynthide, E. Pil. Rhei comp. L. E. Pil. Sagapeni comp. L. Pil. Scammonii comp. cum Aloe, D. Extractum Aloes purificatum, L. Extractum Aloes, D. Pilulce Colocynthidis comp.D. Tinctura Aloes, L. E. D. Tinct. Aloes comp. L. E. D. Tinct. Aloes aetherea, E. Tinct. Ber-zoini comp. L. E. D. Tinct. Rhei et Aloes, E. Vinum Aloes, L. E. D. Decoctum Aloes comp. L. D.