This drug is derived either from the northern and northwestern parts of America, or from Russia, and is called in commerce, according to its source, Canadian or American or Russian castor. It is supposed by some that the American and Russian beavers are distinct species, the former being a building, the latter a burrowing animal, and additional ground for the supposition is afforded by the fact that the products of the two differ considerably. Of the Russian castor only a very small portion is imported into this country.

Castor comes to us in the form of solid unctuous masses, contained in sacs about two inches in length, larger at one end than at the other, much flattened and wrinkled, of a brown or blackish color externally, and united in pairs by the excretory ducts which connect them in the living animal. In each pair one sac is generally larger than the other. They are divided internally into numerous cells, containing the castor, which, when the sacs are cut or torn open, is exhibited of a brown or reddish-brown color, intermingled more or less with the whitish membrane forming the cells. Those brought from Russia are larger, fuller, heavier, and less tenacious than the American; and their contents, which are of a rusty or liver color, have a stronger taste and odor, and are considered more valuable as a medicine.

A variety of Russian castor, described by Pereira under the name of chalky Russian castor, is in smaller and rounder sacs than the American, has a peculiar empyreumatic odor very different from that of the other varieties, breaks like starch under the. teeth, and is characterized by effervescing with diluted hydrochloric acid. Mailer found 40.646 per cent, of calcium carbonate. According to Kohli, Canadian castor, treated with distilled water and ammonia, affords an orange precipitate, while the precipitate thrown down from the Russian under similar treatment is white.

Good castor has a strong, fetid, peculiar odor; a bitter, acrid, and nauseous taste, and a color more or less tinged with red. It is of a softer or harder consistence according as it is more or less thoroughly dried.

When perfectly desiccated, though still slightly unctuous, it is hard, brittle, and has a resinous fracture. Its chemical constituents, according to Brandes, are volatile oil, 2 per cent.; resinous matter, 14-50 per cent.; albumin; a substance resembling osmazome; mucus; salicin; cholesterin; calcium urate, carbonate, benzoate, phosphate, and sulphate; sodium acetate and chloride; potassium chloride, sulphate, and benzoate; ammonium carbonate; membranous matter, and a peculiar proximate principle discovered by Bizio, an Italian chemist, and called by him castorin. For additional information concerning castor, see U. S. D., 19th edition, p. 1435.

Castor was at one time much used as a stimulant antispasmodic, also as an emmenagogue, but has passed almost entirely out of vogue except in perfumery where the alcoholic solution is used in the same manner as preparations of musk and civ&t. It may be given in hysterical affections in doses of ten to thirty grains (0.65-2.0 Gm,), in capsules or emulsion.

A substance allied to castor is the secretion of the anal glands, used for the purpose of defence by the Mephitis mephitica, or common skunk of North America. According to T. B. Aldrich, this is a neutral, golden-colored liquid, having an extremely penetrating and disagreeable odor, containing mercaptan, allyl-sulphide, and traces of butyl-mercaptan. (C. D., 1897.)