Castor is a product of the beaver, Castor Fiber of naturalists. In this animal, in both sexes, there are two pairs of follicles or small sacs, situated between the anus and external genitals, of which the lower and larger contains the castor. After death, this is removed and dried, the pair being still connected by a slender cord, which is their excretory duct.

Two varieties of castor are recognized in the books, one collected in Russia, the other in the northwestern parts of this Continent, distinguished as the Russian, and American or Canadian castor. The latter alone is used in this country.


The two sacs composing the pair are of unequal size, the larger being usually two inches or more in length. They are pear-shaped, but much flattened and wrinkled, brown or blackish externally, and internally divided by a whitish membrane into cells, which contain the castor. This is softish when fresh, but hardens with time, and then, though somewhat unctuous to the touch, is brittle, and exhibits when broken a resinous lustre. Its colour is brown or reddish-brown; its odour strong, fetid, and peculiar; and its taste, bitter, acrid, and disagreeable. It yields its virtues to alcohol or ether, but not to water. Upon distillation it yields a little volatile oil, having its characteristic odour and taste, and upon which possibly its virtues may depend; but this point has not been decided.

Castor deteriorates by time, but very slowly if kept in a cool, dry place. Exposed to heat and moisture, it speedily undergoes decomposition.

Effects on the System

From the small doses in which castor is usually given as a medicine, no observable effect is experienced unless occasionally unpleasant eructations. Mr. Alexander states, in his experimental essays, that he took two drachms of it, at various doses, without any other effect than this. Jorg and his pupils experienced only slight uneasiness of the stomach, with disagreeable eructations. Thouvenal, however, found it, in the quantity of about half an ounce, to increase the frequency of pulse and heat of skin, and to produce other excitant effects. If a stimulant, therefore, to the circulation, it is a very mild one; but it must not be inferred that it is inert as a medicine; for the influence of the class of medicines now under consideration upon the nervous system is, in no degree, measured by that which they may exercise upon the heart and arteries; nor is their remedial power in nervous diseases to be measured by their apparent effect in health; so that the efficiency of castor as a medicine must be decided solely upon the ground of experience. This would seem to have determined in its favour, if medical testimony is to be admitted as having any authority; yet the medicine is certainly not very powerful.

Therapeutic Application

Castor was used by the ancient Greeks, and has ever since held its place in the Materia Medica catalogues. It was anciently employed chiefly in hysteria and amenorrhoea. By modern physicians it has been given in most of the nervous diseases, already enumerated as affording indications for the nervous stimulants. At present it is probably most used to relieve the disordered nervous phenomena of low fevers, and in the different phases of hysteria especially when associated with suppression or retention of the menses. Trousseau and Pidoux speak in decided terms of its utility in amenorrhoea, attended with painful tympanites, and in hysterical colic, with paleness, cold sweats, and sudden prostration. In the North of Europe it is said to be used for promoting labour, and the expulsion of the placenta. I can say nothing of it from experience, having very seldom used it.

The dose of ten or twenty grains, usually mentioned in the books, is probably too small, and may be at least doubled. It may be given in pill or emulsion.

Tincture of Castor (Tinctura Castorei, U. S, Br.) is prepared with undiluted officinal alcohol, and given in doses varying from thirty minims to two fluidrachms, which might be doubled, should the quantity of alcohol not be contraindicated.

An Ammoniated Tincture (Tinctura Castorei Ammoniata, Ed.) was directed by the Edinburgh College, but has been omitted by the British Pharmacopoeia. It was made with assafetida, castor, and the spirit of ammonia of that College, itself a very active stimulant. It was no doubt an energetic antispasmodic and stimulant; but owed its powers much less to the castor than the other ingredients. It might be used in spasm of the stomach, and other nervous affections demanding active stimulation. The dose would be from thirty minims to two fluidrachms.