Active Ingredients. - The resin of the vulgaris, when pulverized, is of a dirty yellow color, always presenting a dull appearance; even thin laminae are very opaque. The odor is excessively disagreeable, and is intensified by breathing upon the lump, which in fracture is imperfectly conchoidal. Proof spirit dissolves nearly the whole. Socotrine aloes give a resinous or vitreous fracture; thin layers are sometimes translucent; the odor, instead of being repulsive, is aromatic; when powdered, the color is bright yellow, and in proof spirit the solution is complete. No difference is perceptible in the bitterness of the two varieties.

The most important constituent of aloes of either kind appears to be aloine, C17H18O7 a neutral and very bitter substance, which crystallizes in needles, is insoluble in cold alcohol, and very sparingly soluble in cold water. In either fluid, however, when warmed, it is readily soluble; and if heated to 212°, it rapidly oxidizes and decomposes. Aloine is likewise soluble in alkaline fluids, forming with them a yellow solution which gradually darkens in color.

Aloes also contain a resinoid substance, which differs from all ordinary resins in being soluble in boiling water, and which is formed probably by atmospheric action upon the aloine. Aloetic acid likewise occurs, striking, with the persalts of iron, an olive-brown. The action of nitric acid upon aloes gives rise to the acids named polychromic, chrysammic, and chrysolepic, all of which are crystalline substances. The colors of their solutions are red and purple.

Physiological Action. - By whatever means introduced into the system, aloes have a laxative action. Whether swallowed, or injected by the rectum, or injected subcutaneously, or rubbed into the skin, the operation is the same; and it may be added that nursing mothers who take aloes communicate the laxative effect to the infants that imbibe the milk. Cullen believed that the specific action of aloes was exercised solely upon the colon and rectum and that the drug was a simple evacuant of the feces. Wede-kind, on the other hand, held that the primary action is to increase the secretion of bile, and that the purgative or laxative effects are secondary. I lean to the opinion that Wedekind was right; and I further believe that it is the secondary action which excites the power of the muscular coat of the colon and of the rectum; and that it is by this increased muscular action that the feces are expelled, rather than that the expulsion takes place through the hyper-secretion which is thrown out from the mucous surfaces of the intestines mentioned. Aloes, no doubt, cause augmentation of the mucous secretion of the colon and rectum; but what we have carefully to remember is that the good effects of the medicine are owing, as before stated, not to this simple augmentation of mucus, but to the prior increase in the flow of the bile,1 and the excitation of the action of the muscular coat.

When aloes are resorted to as an habitual laxative they produce dryness of the throat, an unpleasant sense of warmth throughout the abdomen, with uneasiness amounting almost to pain in the hepatic region, and a tightness and throbbing in the right hypochondrium. The whole of the pelvic viscera are brought into a more or less engorged or congested condition, and in the portal system there is likewise a tendency to congestion. These symptoms are accompanied by heat, irritation, and tenesmus in the rectum, often with subsequent haemorrhoids; the bladder becomes irritated; the urine hot and scanty. In women the menstrual secretion is, under ordinary circumstances, greatly augmented; and when the secretion is absent, or nearly so, the natural flow is restored. Aloes also have the property, when taken in small and repeated doses, of increasing sexual desire (Stille). The pulse, as a rule, is slightly quickened.

Administered as a medicine, a dose of one to five grains of aloes acts upon the bowels in from eight to twelve hours. A dose of this description does not produce nausea or any general disturbance, although usually causing irritation, and a sense of warmth throughout the abdomen. The evacuation of the bowels is generally attended by griping pains; the stools are copious, but not too abundant; there is usually only one, or at all events there are not more than two. They are fasculent, and of a dark brownish yellow color, and have a characteristic odor. The number of motions depends more upon the condition of the bowels, i.e. to what degree they are loaded, than upon the strength of the pill; for it is well known that a single grain of aloes often acts as powerfully as five grains will.

1 It is right to mention that several recent observers, of good repute, deny this action on the liver; and Nothnagel says there are "no convincing proofs of it." I nevertheless hold to the above opinion, from my own observation of the character of the stools.

Therapeutic Action - Aloes, in small doses, operate as a warm and stimulating purgative, particularly adapted to the temperament called the melancholic. They also exert a tonic power, and hence have a very beneficial influence in chronic affections of the stomach and bowels, such as loss of appetite, flatulence, constipation, and others usually denominated dyspeptic. The operation is slow, but generally effectual; and as before observed, large doses do not appear to exert any greater influence than small ones. Acting more particularly upon the colon and the rectum, aloes are efficacious also in expelling ascarides; but for the same reason they are said to occasionally produce haemorrhoids: this idea has, however, been rejected by many good observers, who maintain that the aloes never caused the piles, which existed already; and on the contrary, aloes often cure piles by removing constipation. In dysenteric diarrhoea, verging into the chronic stage, and attended by tenesmus, I have used aloes with excellent effect; they probably do good by substituting regular and rhythmical peristaltic action for the spasmodic condition which produces tenesmus and prevents the bowel being effectually evacuated. Aloes are well adapted for use in jaundice, especially when there is hypochondriasis.

Chronic Constipation is often very effectively dealt with by means of aloes; and there is a particular plan introduced by Dr. J. K. Spender, of Bath-, which deserves notice. Dr. Spender gives a pill containing one grain watery extract of aloes and two grains sulphate of iron; this is administered, at first three times, then twice, and then once daily. We must not be impatient in administering aloes in this way; it may take some days, or even two or three weeks, to produce a decided effect, but the desired result is usually attained in the end.

As an Emmenagogue, aloes have had a great reputation, but have often been indiscriminately employed in a routine way which is not justified by what we know of the physiological action. Given at chance times, aloes (as Graves pointed out) are no more likely to restore defective menstruation than any other ordinary purgative. Indeed they are likely to do special mischief; inasmuch as they certainly do tend more than other aperients to engorge the pelvic viscera, and it is very undesirable that this should be done except at stated times. Graves points out that in nearly all cases of amenorrhcea there are abortive efforts at the performance of the function, which may be traced in the periodical recurrence of pain in the loins, thighs, and hypogastric regions, flushing, etc. It is at these times, only, that we should administer such substances as cause a direct flow of blood to the uterus; at any other times the congesting influence will only do harm, because the ovarian disposition to menstruation does not exist. Pregnant women should beware of using aloes as an aperient, though it is doubtless true that aloes have sometimes cured piles in pregnancy, by removing constipation.

The medicinal effects of the two kinds of aloes, the Barbadoes and the

Socotrine, differ but little. The Barbadoes are said to be more energetic, for which reason they are used by veterinary surgeons, who find the action to take place upon horses in from twelve to twenty-four hours.

Preparations and Dose. - Aloe, gr. ss. - v. (.03 - .30); Piluhe

Aloes, No. 1 - 3; Pil. Aloes et Assafoetidae, No. 1 - 3; Pil. Aloes et Mas-tiches, one after meals. Pil. Aloes et Myrrhae, No. 1 - 3; Pulvis Aloes et Canellae, gr. i - v. (.06 - .30); Tinct. Aloes et Myrrhae, 3 ss. - j. (2. - 4.); Vinum Aloes, 3j- (4.); Suppositoria Aloes.