Oak Bark.
Qualities. Odour, none; taste, rough and astringent. Chemical Composition. We are indebted to Sir H. Davy for a knowledge of this subject; he found that an ounce of the inner cortical part of young oak bark afforded by lixivation 111 grains of solid matter, of which 77 were tannin; and the cellular integument, or middle-coloured part, only yielded 43 grains of solid matter, of which 19 were tannin; and the epidermis furnished scarcely any quantity of tannin or extractive; hence the bark should be selected from the smaller branches of the oak where the epidermis is still thin. Experience has, moreover, shewn that the quantity of tannin varies considerably, not only according to the age and size of the trees, but according to the season at which they are barked; thus, the bark cut in spring contains, according to Beguin,[[620]] four times more of the astringent principle, than that which is obtained in winter. Med. Uses. All its properties depend upon the presence of tannin, it is therefore only valuable as a powerful astringent; it is accordingly employed to check inordinate discharges, see Decoctum Quercus. Oak bark is sometimes administered in the form of powder, combined with ginger and other aromatics, and bitters, for the cure of intermittents, and it has frequently succeeded, but see page 167. Dose, ℈j to ʒss. In the form of poultice this powder is said to have proved highly useful to gangrenous sores. Its inhalation has also been supposed to prove beneficial in consumption; a striking case is related by Dr. Eberle of a man who had laboured under the usual symptoms of confirmed Phthisis, and who, at the time he went to grind in a bark-mill, was extremely weak and emaciated; in a short time, however, the cough, night sweats, and other hectic symptoms, began to abate sensibly, and in less than three months he was perfectly restored to health.
RHEI RADIX. L.E.D. Rhubarb.[[621]]
Two varieties of this root are known in the shops, viz. Turkey or Russian, and East Indian or Chinese.
1. Turkey or Russian. (Rheum Palmatum.)
Qualities. Form, small round pieces, rather compact and heavy, perforated in the middle; Colour, lively yellow with streaks of white; it is easily pulverized, affording a powder of a bright buff-yellow colour. Chemical Composition. Gum, resin, extractive, tannin, gallic acid, and a peculiar colouring matter, with traces of alumina and silex; the white or flesh-coloured streaks pervading its substance, consist of sulphate and oxalate of lime: according to the experiments of Mr. John Henderson, there is besides a peculiar vegetable acid, to which he has given the name of Rheumic acid, but M. de Lassaignes has satisfactorily proved that this is no other than the oxalic acid: the purgative powers of the root appear to be intimately connected with its extractive and resinous elements, but the subject is still involved in considerable obscurity. Solubility. Water at 212° takes up 24 parts in 60, see Infusum Rhei: by decoction, its purgative qualities are lost, and it becomes more bitter and astringent; alcohol extracts 2·7 from 10 parts, (see Tinct. Rhei.) Med. Uses. In this substance, Nature presents us with a singular and most important combination of medicinal powers, that of an astringent, with a cathartic property; the former of which never opposes or interferes with the energy of the latter, since it only takes effect when the substance is administered in small doses, or if given in larger ones, not until it has ceased to operate as a cathartic; this latter circumstance renders it particularly eligible in cases of diarrhœa, as it evacuates the offending matter before it operates as an astringent upon the bowels. It seems to act more immediately upon the stomach and small intestines, and therefore in relaxed and debilitated states of these organs, it will prove an easy and valuable resource; it may, for such an object, be exhibited in conjunction with alkalies, bitters, and other tonics. Its cathartic property is most efficient when given in substance. It was formerly supposed that by toasting rhubarb we increased its astringency, but this process merely diminishes its purgative force, so that a larger dose may be taken. The colouring matter of rhubarb may be detected in the urine of persons to whom it has been exhibited; it does not however appear to possess any specific powers as a diuretic. Dose, grs. vj to x as a tonic; ℈j to ʒss as a purgative; the operation of which is considerably quickened by the addition of neutral salts; the super-sulphate of potass forms also a very useful adjunct, and its acidulous taste completely covers that of the rhubarb. Form. 83, 85. Its powder, when sprinkled upon ulcers, is found to promote their healthy granulation. Off. Prep. Infus: Rhei. L.E. Vinum Rhei Palmati. E. Tinct. Rhei. L.E.D. Tinct. Rhei. comp. L. Tinct. Rhei cum Alöe. E. Tinct. Rhei cum Gentian. E. Pil. Rhei comp. E.
2. East Indian, or Chinese. (Rheum Undulatum?)[[622]]
Qualities. Form, long pieces, sometimes flat, as if they had been compressed; they are heavier, harder, and more compact than those of the preceding species, and are seldom perforated with holes; Odour, stronger; Taste, more nauseous; white streaks less numerous, and they afford a powder of a redder shade than those of Turkey rhubarb. Chemical Composition. It differs from the Turkey in containing less tannin and resin, and according to the experiments of Mr. A. T. Thomson, less oxalate of lime, in the ratio of 18 to 26. It contains however more extractive and gallic acid. Solubility. Water takes up one half of its weight, but the infusion, although more turbid, is not so deep coloured as that of Russian rhubarb; alcohol extracts 4 parts in 10. It habitudes with acids, alkalies, and neutral salts, differ likewise from those of the Russian variety, as Mr. A. T. Thomson has exhibited in a very satisfactory manner. (London Dispensatory, Edit. 3, p. 474.) Adulterations. The inferior kinds of Russian, East Indian, and even English rhubarb, are artfully dressed up and sold under the name of Turkey rhubarb. I am well informed that a number of persons in this town, known in the trade by the name of Russifiers, gain a regular livelihood by the art of dressing this article, by boring, rasping, and then colouring the inferior kinds; for which they charge at the rate of eighteen-pence per pound. The general indications of good rhubarb are, its whitish or clear yellow colour, and its possessing the other characteristic properties as above mentioned; it ought also to possess in an eminent degree the peculiar odour, for when this is dissipated, the powers of the medicine are nearly destroyed. In the form of powder, rhubarb is always more or less mixed with foreign matter; the detection of which can be alone effected by a trial of its efficacy.
RICINI[[623]] OLEUM. L.E.D. (Ricinus Communis.)
Castor[[624]] Oil.