There are few subjects in the materia malice which are so enveloped in obscurity as rhubarb. Even the period of its introduction into medicine is uncertain, for the &scrip t:on given by Dioseorides of the drug which he designates rheon does not correspond with our rhubarb. It was probably introduced into Europe by the Arabian physicians, somewhat previous to the time of Avicenna, iu whose writings the term Teuetnd occurs mune still used, with a slight alteration, for rhubarb by the Persians and Hindus. In the British pharmacopmia no attempt is made to determine the species of rhcian used in medicine, and there can be no doubt that the roots of several species arc usually to be found in the drug-mark• According to the pharmacopoeia, the root, deprived of its ball:. is imparted from "Chinese Thibet and Tartary." Little is known of the chem ical composition of rhubarb root further than that it yields a yellow coloring matter termed rbeil. (C2olIs0.?). which is sparingly soluble in water, but dissolves freely in the producing a reddish-brown liquid, from which the rhein may be precipitated in flakes on the addition of acetic acid. Rhubarb is very liable to adulteration; and if the adulterated rhubarb be in a state of powder, the detection of the fraud is very difficult.
Rhubarb may be briefly described as a cathartic, an astringent, and a tonic. As a cathartic it chiefly operates by increasing the muscular action of the intestines; and when the cathartic action is over, there is generally more or less constipation, arising, as is usually, supposed, from the astringent action then coming into play. The appetite is also improved, and the digestive process rendered more active, by the action of this drug. It mnst not be forgotten that the coloring matter of rhubarb passes into the
serum of the blood and the secretions; and urine rendered red by its absorption has not unfrequently been confounded with bloody urine by practitioners ignorant of the very different chemical reactions of litchi and the coloring matter of blood.
Rhubarb is one of the best aperients for general use in infancy. in consequence of tile certainty of its action, akad of its tonic and astringent properties, which are of Dutch importance in the treatment of many infantile diseases, attended with imperfect diges tion and irritation of the intestinal canal. In adults it is serviceable in chronic diarrhea and dysentery, when it is expedient to clean out the bowels. It is also a useful aperient in convalescence from exhausting disease, as being free from the risk of overacting: and for the same reason it is a useful medicine for persons who are constitutionally liable to over-purgatiou from trivial causes.
The officinal preparations are the pelvis rhei composites (composed of powdered rhu barb. magnesia, and ginger, and popularly known as Gregory's powder or mixture—the average dose being a teaspoonful), the pilule rlui conpweta (a compound rhubarb-pill, composed of rhuharh, aloes, myrrh, hard soap, oil of peppermint, and treacle—time dose. as an aperient. being ten or fifteen grains), the exileveum rhei, (dose from five to ten grains). the Wesem rhei (dose from two to four fluid-ounces), and the tinetere rhei, which is usually given in doses of about a dram, in association with other aperients.