Rhubarb: a plant with large dock-like leaves, among which arises a single thick stalk bearing loose clusters of naked monopetalous bell-shaped flowers divided into six segments: each flower contains nine stamina (whereof the docks strictly so called have but six), and is followed by a triangular seed surrounded about the edges with a leafy margin.

1. Rhabarbarum Pharm. Lond. Rheum Pharm. Edinb. Lapathum orient ale folio latiffimo undulato & mucronato Mill. dict. Rheum undu-latum foliis subvillofis, petiolis aequalibus Linn. Rhubarb: with the leaves somewhat heart-shaped, acuminated, and slightly hairy, and the pedicles plano-convex. It is a native of China and Siberia, and has lately been raised in some of our gardens, where it is found to grow with vigour in the open ground (a).

(a) The plant above described is that which is generally reckoned the true rhubarb plant, having been produced from the seeds, sent from Russia, as those of the true rhubarb to Juffieu at Paris, Rand at Chelfea, and Linnaeus at Upfal,

Two sorts of rhubarb roots are met with in the shops. The first is imported from Turkey and Russia, in roundish pieces, freed from the bark, with a hole through the middle of each, externally of a yellow colour, internally variegated with lively reddish streaks. The other. which is less esteemed, comes immediately from the East Indies, in longish pieces, harder, heavier, and more compact than the foregoing. The first sort, unless kept very dry, is apt to grow mouldy and worm-eaten: the second is less subject to these inconveniencies. Some of the more indufsrious artists are said to fill up the worm holes with certain mixtures, and to colour the outside of the damaged pieces with powder of the finer sorts of rhubarb, and some-times with cheaper materials. The marks of the goodness of rhubarb are, the liveliness of its colour when cut; its being firm and solid, but not flinty or hard; its being easily pulverable, and appearing when powdered of a fine bright yellow colour; its imparting to the spittle, on being chewed, a deep saffron tinge, and not proving flimy or mucilaginous in the mouth. Its taste is fubacrid, bitterish, and somewhat flyptic; the smell, lightly aromatic.

Rhubarb is a mild cathartic, and commonly looked upon as one of the safest and most innocent of the substances of this class. Besides its purgative virtue, it has a mild astringent one, discoverable by the taste, and by its strik-ing an inky blackness with chalybeate solutions: hence it is found to strengthen the tone of the stomach and intestines, to leave the belly costive, and to be one of the most useful purgatives in diarrhoeas, dysenteries, and all disorders proceeding from a debility and laxity of the fibres: it is frequently indeed given with a view rather to this stomachic and corroborating virtue, than to its producing any considerable evacuation. It tinges the urine of a high yellow colour.

Upfal. Dr. Hope received lately rhubarb seeds from the same country, which being sown in the open ground at Edinburgh, produced a different species, Rheum palmatum Linnaei, with the leaves deeply cut into pointed segments. He observes that the root of this plant, though taken up too young, and at an improper season, viz. in July, agreed perfectly with the best foreign rhubarb, in colour, smell, taste, and purgative quality. See Philosoph. Transact, vol. Iv. for the year 1765. - Perhaps the roots of both species • may be of the same quality, and taken promiscuously.

Rhubarb in substance purges more effectually than any preparation of it: the dose is from a scruple to a dram. By roasting it with a gentle heat, till it becomes easily friable, its cathartic power is diminished, and its astringency sup-posed to be increased.

In its habitude to menstrua, it differs remarkably from most of the other cathartic drugs, its purgative virtue being extracted far more perfectly by water than by rectified spirit: the root remaining after the action of water is almost, if not wholly, inactive; whereas, after repeated digestion in spirit, it proves {till very considerably purgative: the colour of both tinctures is a fine deep yellow, that of the spirituous palest; when the rhubarb has given out to spirit all that this menstruum can extract, it (till imparts a deep colour, as well as a purgative impregnation, to water. The watery infusion, in being inspiffated by a gentle heat, has its virtue so much diminished, that a dram of the extract is said to have scarcely any greater effect than a scruple of the root in substance: the spirituous tincture looses less; half a dram of this extract proving moderately purgative, though scarcely more so than an equal quantity of the powder. The spirituous extract dissolves almost wholly in water; and hence the tincture does not, like the spirituous infusions of rnost other vegetables, turn milky on being mixed with aqueous liquors: of the watery extract, scarce above one fourth is dissolved by rectified spirit, and the part that does not dissolve proves more purgative than that which does.

Rhabarb. torrefactum.

* A watery infusion is directed in the Edinburgh pharmacopoeia, made by infusing half an ounce of rhubarb for a night in eight ounces of boiling water, and adding to the strained liquor one ounce of spirituous cinnamon water. The London has a more compound and warmer infusion, in which an ounce of rhubarb, with a dram of ginger, a dram of saffron, and two drams of liquorice root, are digested for a fortnight in half a pint of water and six ounces of proof spirit.

Tinctures of this root are drawn in the shops with proof spirit and with mountain wine. The London college directs an ounce of rhubarb with two drams of cardamom seeds, and one of saffron (a) for a pint of each tincture†: that of Edinburgh, orders for the vinous tincture, two ounces of rhubarb and one dram of canella alba to be infused in fifteen ounces of mountain wine, and two of proof spirit ‡; for the simple spirituous tincture, three ounces of rhubarb, and half an ounce of lesser cardamom seeds, to two pounds and a half of proof spirit ||; in which, sometimes are dissolved, four ounces of sugar candy §; and a compound tincture, composed of two ounces of rhubarb, half an ounce of gentian, one dram of snakeroot, and two pounds and a half of proof spirit ††. These preparations are used chiefly as mildly laxative corroborants, in weakness of the stomach, indiges-tion, diarrhoeas, colicky and other like complaints. The last tincture is, in many cases, an useful assistant to the Peruvian bark in the cure of intermittents.

(a) Saffron does not appear to be a vety proper ingredient in these preparations, as it renders the taste rather more unpleasant; nor indeed does rhubarb seem, for general use, to want any aromatic addition, posed

Infuf. rhei Ph Ed.

Tinct. rha-barb. comp. Ph. Lond.

†Tinct: rha-barb. vinum Rhabarb. Ph. Lond.

‡ Vinum rhei Ph. Ed.

|| Tinct. rhei.

§ Tinct, rhei dulcis.

The Turkey rhubarb is, among us, univer-sally preferred to the East India sort, though this last appears to be for some purposes at least equal to the other. It is manifestly more astrin-gent, but has somewhat less of an aromatic flavour. Tinctures made from both with equal quantities of rectified spirit, have nearly the same taste: on drawing off the menstrua, the extract left by the tincture of the East India rhubarb proves in taste considerably stronger than the other. Both sorts appear to be the produce of the same climate, and the roots of the same species of plant, taken up probably at a different season, or cured in a different manner.

2. Rhaponticum Pharm. Paris. Rhabar-barum dioscoridis & antiquorum Fount. Rhaponticum folio lapathi majoris glabro C. B. Rheum Rhaponticum Linn. Rhapontic: with smooth roundish leaves, and somewhat channelled pedicles. It grows wild on the mountain Rho-dope in Thrace, from whence it was brought into Europe by Alpinus about the year 1610: it bears the hardest winters of this climate.

The root of this plant, which appears to have been the true rhubarb of the ancients, is by some confounded with the modern rhubarb, though considerably different from that root in appearance as well as in quality. The rhapontic is of a dusky colour on the surface, and a loose spongy texture; more astringent than rhubarb, and less purgative: in this last intention two or three drams are required for a dose.

†† Tinct. rhei amara Ph. Ed.