POLYGONACEiE. 545 



there is the same crackling on chewing it, and the same colour imparted to 

 the saliva ,* the powder is usually of a brighter yellow than in the last 

 variety. 



The Buchanan Rhubarb seems to be an inferior quality of the Russian. 

 The Siberian, which is in cylindrical pieces, is probably the product of R. 

 rhaponticum. Of late years, Rhubarbs from Himalaya species have been 

 tried in India, and found of excellent quality, and may perhaps hereafter 

 become an article of commerce. The French and English Rhubarbs are of 

 inferior quality, and are seldom employed in this country, as the Chinese is 

 plentiful and at comparatively a low price. 



Numerous analyses of Rhubarb have been made, and it has been found to 

 owe its properties to the presence of Chrysophanic acid, which in its impure 

 state has been described by Brandes as Rhabarberic acid, as Rhabarbarin by 

 Geiger, and Rhein and Rheumin by other authors ; to a mixture of several- 

 resins and Extractive matter ; the active principles are taken up by water and 

 by alcohol ; with the alkalies it produces a red-coloured solution. 



Medical Uses. — Rhubarb is a mild and safe purgative, and at the same 

 time is gently astringent and tonic. Its colouring matter is rapidly absorbed, 

 and tinges the urine and other secretions of a yellow colour. As a purgative 

 it is in general use, and is well adapted to delicate persons and children, where 

 it is wished to evacuate the bowels without exciting an undue action in them. 

 It is much employed in dyspepsia attended with constipation, and forms the 

 basis of most of the preparations known as " dinner pills," &c. It is either 

 given alone or in a variety of combinations, as with soap, to counteract its 

 astringent quality, with magnesia to increase its action, or where acidity ex- 

 ists. When toasted, much of its purgative power is destroyed, but its astrin- 

 gency remains the same. 



The preparations of it are very numerous. It is given in powder in doses 

 of from five grains to half a drachm, according to the indication to be fulfilled. 

 The usual purgative dose is from ten to twenty grains. (See Amer. Dispen., 

 Pereira, and Royle.) 



Rumex. — Linn. 



Calyx of three obtuse, spreading, persistent sepals, more or less combined at base, and 

 of three ovate, larger, internal ones, thinner in texture, but of the same colour, finally in- 

 creased in size and eonnivent ; in some species having a dorsal gland or tubercle. Sta- 

 mens six. Filaments very short, capillary. Anthers oblong, erect, with two lobes. Styles 

 four, capillary, with large stigmas, in numerous fine, tufted segments. Nut triangular, 

 superior, naked. Embryo oblong, on one side of the albumen. 



An extensive genus, found in Europe, the temperate parts of Africa, and 

 in the United States. The species have terminal or axillary paniculate flow- 

 ers, and in some cases are monoecious or dioecious. The roots are generally 

 large and fleshy, and are usually astringent, but sometimes purgative. R. 

 crispus, a native of this country, is said to be useful in decoction or ointment, 

 in the treatment of itch ; the part used is the root ; that of R. obtusifolius has 

 the same properties, and that of R. patie?itice is much employed in France as 

 a depurative remedy in cutaneous disorders, scurvy, &c. ; it is also consi- 

 dered to be tonic and stomachic. The leaves of this and several other of the 

 species are used as greens ; R. sanguineus is also thought to be useful as an 

 astringent in hsemorrhagies, and that its juice was a beneficial application to 

 cancerous ulcers. 



The most active species is unquestionably R. alpinus, a native of the moun- 



35 



