Castor consists of the dried preputial or vaginal follicles of the beaver, Castor Fiber, Linn. (Order Rodentia), an animal found chiefly in the Hudson Bay Territory, but also in Western Russia and Siberia. The glands are obtained from both the male and female animals, and dried. The drug occurs in dark brown or greyish pear-shaped masses, about 5 to 7.5 centimetres long, often in pairs, connected by a dried strip of the preputial or vaginal canal. They are firm, heavy, and solid, have a characteristic odour, and are divided internally into numerous cells, which contain a resinous secretion, in which, when examined microscopically, spherical grains of calcium carbonate can be observed; this secretion is yellowish and creamy in the fresh sac, but becomes darker and resinous on keeping, hence the appearance of the contents of the sacs may vary considerably in colour and consistence. Occasionally the contents of the sacs are sophisticated by fraudulent addition of dried blood, resin, etc.
Constituents.—The composition of the drug varies considerably, the chief constituent being 40 to 70 per cent. of resinous matter soluble in alcohol; salicin, benzoic acid, and a crystalline substance named castorin are also said to be present. The characteristic odour is due to the presence of a volatile oil.
Action and Uses.—Castor has long had a reputation in the treatment of dysmenorrhoea and hysterical conditions. It has an important action on the circulation, increasing the output from the heart and raising blood pressure, so that of late years it has come to be used in certain conditions of "flabby" heart which are not benefited by digitalis and its allies. It is administered principally as Tinctura Castorei, which may be given in mixture form with a little mucilage to suspend the resin, and tincture or infusion of valerian. On account of its nauseous taste, the tincture is sometimes prepared in capsule form, a portion of the spirit being removed by evaporation.
- Tinctura Castorei, B.P.C.—TINCTURE OF CASTOR. 1 in 20.
- Mixtures containing this tincture require the addition of one-sixteenth of their bulk of mucilage of gum acacia. Dose.—2 to 4 mils (½ to 1 fluid drachm).