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Jhe Materia Medica.

Part II.

RAPI radix, femen: Rapt fatiuirotundi C. B. Turneps ; the rootsand feeds [£.]

Thefe roots are accounted awholefome aperient food: the li-quor preffed out from them afterboiling has been fometimes ufedmedicinally as a deobftruent anddiuretic. The feeds are flightlypungent.

REALGAR, a foflil compofedof arfenic and fulphur. VideArsenicum.

REGINA PRATI, vide U l -

MARIA.

RHABARBARUM [L.E.]Rhubarb; the root of a plant of thedock kind, which grows fpontane-oufly in China, and endures thecolds of our own climate. T woforts of rhubarb are met with inthe fhops. The firft is importedfrom Turkey and Ruffia, in round-ifh pieces freed from the bark,with a hole through the middle ofeach ; they are externally of a yel-low colour, and on cutting ap-pear variegated with lively reddifhftreaks. The other, which is lefsefteemed, comes immediately fromthe Eaft- Indies, in longilh pieces,harder, heavier, and more compadtthan the foregoing. The firft fort,unlefs kept very dry, is apt togrow mouldy and worm-eaten ; theiecond is lefs fubjett to thefe incon-veniencies. Some of the more in-duftrious artifts are faid to fill upthe worm holes with certain mix-tures, and to colour the outfide ofthe damaged pieces with powder ofthe finer forts of rhubarb, and fome-tifiies with cheaper materials: thisis often fo nicely done, as effec-tually to impofe upon the buyer,unlefs he very carefully examineseach piece. The marks of goodrhubarb are, that it be firm andfolid, but not flinty ; that it be ea-£ly pulverable, and appear, when

powdered, of a fine bright yellowcolour : that upon being chewed,it imparts to the fpittle a faffrontinge, without proving flimy ormucilaginous in the mouth. Itstafte is fubacrid, bitterifh, andfomewhat aftringent; the fmelllightly aromatic.

Rhubarb is a mild cathartic*which operates without violenceor irritatioh, and may be givenwith fafety even to pregnant wo-men and children. Befides its pur-gative quality, it is celebrated foran aftringent one, by which itltrengthens the tone of the ftomachand inteftines, and proves ufeful indiarrhoea; and diforders proceedingfrom a laxity of the fibres. Rhu-barb in fubftance operates morepowerfully as a cathartic than anyof the preparations of it. Waterytin&ures purge more than the fpi-rituous ones; whilft the latter con-tain in greater perfeftion the aro-matic,aftringent,and corroboratingvirtues of the rhubarb. The dofe,when intended as a purgative, isfrom a fcruple to a dram or more.

The Turkey rhubarb is, amongus, univerfally preferred to theEaft-India fort, though this laft isfor fome purpofes at leaft equal tothe other; it is manifeftly moreaftringent, but has fomewhat lefs ofan aromatic flavour. Tintturesdrawn from both with reftifiedfpirit, have nearly the fame tafte:on diftilling off the menftruum, theextraft left from the tinfture of theEaft-India rhubarb proved conli-derably the ftrongeft. They are boththe produce of the fame climate,and probably the roots of the fameplant taken up at different feafons,or cured in a different manner.

The officinal preparations of thisdrug are, roafted rhubarb [£.] awatery infufion [£.] and vinousand fpirituous tindures [i. £.] Itis an ingredient in fundry compofi-

tions,