Pulegii Oleum. Oil of Pennyroyal. (Not officinal.) The oil distilled from the flowering plant of Mentha Pulegium, or Pennyroyal; Lin. Syst., Didynamia gymnospermia; indigenous, growing in marshy places.

Prop. & Comp. Oil of Pulegium, is yellowish, sp. gr. 0.95. It is an oxidized oil or hydrocarbon, containing a camphor in solution.

Therapeutics. As oil of mentha piperita, and mentha viridis.

Dose. The same as the oil of mentha piperita, and mentha viridis.

Two other plants belonging to this order, namely, Origanum Vulgare, the Common Marjoram, containing a volatile oil, and possessing properties similar to those of Rosmarinus; and Mar-rubium Vulgare, or Horehound, possessing a bitter principle as well as a volatile oil, were formerly contained in the Pharmacopoeia; the latter is still used in domestic medicine as a tonic, expectorant, and alterative, in phthisis, chronic hepatitis, and in cachexia from various causes.

Sub-Class IV. Apetalae. Polygonaceae.

Rheum. Rhubarb. The root of an undetermined species of Rheum; Lin. Syst., Enneandria monogynia; growing in Chinese Thibet and Tartary. This definition includes the Russian, the East Indian and Dutch-trimmed or Batavian rhubarbs. Many species of Rheum are known to botanists, but although great exertions have been made, as yet the species yielding the Chinese rhubarb has not been discovered.

Description. Russian or so-called Turkey rhubarb occurs in irregular-shaped, flat, or cylindrical, angular pieces, the cortex having been removed by slicing; externally it is smooth and yellow and not turned brown by .boracic acid; the texture is compact; the fracture uneven, and marbled red and grey; the powder is bright buff-yellow, and the odour rather aromatic; taste astringent and disagreeable; it feels gritty, and tinges the saliva bright yellow; the pieces have generally a hole drilled in them.

East Indian, or half-trimmed rhubarb, differs from the last in not being angular, but slightly rounded, with adhering portions of 21 the cortex, as if it had been scraped and sliced; externally it is red and veined, not covered with yellow powder, as the Russian variety; also denser, with a smoother fracture, less gritty, and the powder of a redder hue.

Another variety is called Dutch-trimmed or Batavian rhubarb; in round or flattened pieces, angular, and drilled with a hole; probably of the same origin as the Russian.

Besides these officinal varieties, others are met with, as the Himalayan, Canton stick, and English rhubarb. Some of the Himalayan, according to Dr. Royle, is yielded by Rheum Emodi, Morecroftianum and Webbianum; the English variety is derived from Rheum Rhaponticum, and grows near Banbury.

Prop. & Comp. Rhubarb contains a principle, Rheine or Chry-sqphanic acid, which occurs in crystalline needles of a golden yellow, metallic lustre (C20 H8 O6), sparingly soluble in water, freely so in alkaline solutions, which are of a reddish-brown colour; rheine is soluble also in hot alcohol and ether. Various resins have been also obtained from Rhubarb; but although numerous analyses have been made, the peculiar purgative principle has not yet been isolated. Rhubarb yields its active properties to boiling water, also to alcohol. Crystals of oxalate of lime are found in it in considerable quantities, forming at times in the Russian variety, in which they are most numerous, as much as 35 per cent. of the drug.

Off. Prep. Extractum Rhei. Extract of Rhubarb. (Prepared by macerating one pound of rhubarb in five pints of water and ten fluid ounces of rectified spirit, and subsequent evaporation of the solution at a temperature not above 160°.)

[Extractum Rhei Alcoholicum. Alcoholic Extract of Rhubarb. U. S. Rhubarb, twelve troy ounces; alcohol, a pint; diluted alcohol, a sufficient quantity. A tincture is obtained by percolation, and evaporated at a temperature not exceeding 160° to form an extract.]

Infusum Rhei. Infusion of Rhubarb. (Sliced rhubarb, quarter of an ounce; boiling distilled water, ten fluid ounces.) [Bruised rhubarb, one hundred and twenty grains; boiling water, half a pint. U. S.]

Pilula Rhei Composita. Compound Rhubarb Pill. (Rhubarb, powdered, three ounces; socotrine aloes, powdered, two ounces and a quarter; myrrh, finely powdered, one ounce and a half; hard soap, one ounce and a half; English oil of peppermint, one and a half fluid drachms; treacle, by weight, four ounces.) [Rhubarb, in powder, a troy ounce; socotrine aloes, in powder, three hundred and sixty grains; myrrh, in powder, half a troy ounce; oil of peppermint, half a fluid drachm. Beat them with water so as to form a pilular mass, to be divided into two hundred and forty pills. U. S.]

Pulvis Rhei Compositus. Compound Rhubarb Powder. (Gregory's Powder.) (Rhubarb, two ounces; light magnesia, [magnesia. U. S.] six ounces; ginger, one ounce.)

Tinctura Rhei. Tincture of Rhubarb. (Rhubarb, two ounces; cardamons, quarter of an ounce; coriander, quarter of an ounce; saffron, quarter of an ounce; proof spirit, twenty fluid ounces. Made by maceration and percolation.)

[Rhubarb, three troy ounces; cardamom, half a troy ounce; diluted alcohol, a sufficient quantity. Two pints of tincture are obtained by percolation. U. S.]

Therapeutics. Rhubarb acts as a stomachic and slight astringent in small doses; as a purgative, in larger ones. Its purgative action is generally followed by constipation, dependent on its astringent constituents; it differs from many cathartics in not causing irritation of the alimentary canal. The urine becomes coloured by it, as also do the perspiration and the milk. In consequence of its purgative properties it is often used at the commencement of diarrhoea depending on the presence of irritant matter in the canal, which is thus expelled, and the subsequent astringent effect afterwards exercised proves very valuable. It is frequently combined with magnesia, especially when given to children, as in the form of Gregory's powder. In cases of atonic dyspepsia, attended with some constipation, it is a valuable remedial agent; but if prescribed in cases of habitual constipation, should be combined with some other laxative. In scrofulous children it is sometimes useful, combined with a mercurial alterative, aiding and giving tone to the digestive organs, etc. Externally it has been applied to indolent ulcers.

Dose. Of powdered rhubarb, 1 gr. to 5 gr. as a stomachic; 10 gr. to 30 gr. as a purgative; of infusion, 1 fl. oz. to 2 fl. oz.: of the tincture, as a stomachic, 1 fl. drm. to 2 fl. drm.; as a purgative, 1/2 fl. oz. to 1 fl. oz.; of compound rhubarb pill, 10 gr. to 20 gr.; of the compound powder, 5 gr. to 10 gr. for children; for an adult, 20 gr. to 60 gr. and upwards.

Adulterations. Rhubarb is very often extensively adulterated. Inferior varieties of rhubarb, as the English, are substituted for the Russian, etc. If turmeric be present, it is reddened by boracic acid, which has no such effect upon the colouring matter of rhubarb. In English rhubarb the starch is generally in excess, the oxalate of lime in small amounts only; the proportions of these ingredients are reversed in the Chinese varieties.