464 RHUBARB 



water, forming with the latter an orange-coloured solution. 

 The East Indian rhubarb is coarser and less aromatic. 

 English rhubarb, the produce of R. raponticum, generally 

 cultivated for its familiar leaf-stalks, the pleasant acid taste 

 of which is due to the presence of malic and oxalic acids, is 

 grown extensively for its roots near Banbury, and is some- 

 times mixed with or substituted for the Chinese ; but it is 

 softer and more mucilaginous, has less aroma and grittiness, 

 contains fewer crystals of calcium oxalate, and is deficient in 

 purgative power. 



Rhubarb is one of the anthracene group of purgatives to 

 which belong also senna and aloes. The active principles 

 in these drugs are derivatives of anthraquinone. Among 

 other constituents rhubarb contains (1) ehrysophanie acid, 

 in the proportion of about 2 per cent., extracted by ether or 

 alcohol, insoluble in water, and occurring, as its name 

 indicates, in brilliant yellow crystals. It appears to have 

 tonic properties, and is one of the most effectual remedies 

 for ringworm of the human scalp. (2) Chrysophan, a bitter 

 soluble glucoside, which, when boiled with sulphuric or 

 hydrochloric acid, splits into ehrysophanie acid and sugar. 

 (3) PhSBorretin and other resinous bodies appear to confer 

 the cathartic properties. (4) Rheotannic acid imparts 

 astringency. (5) Mineral substances are largely present, 

 consisting chiefly of calcium oxalate, 35 per cent. 



ACTIONS AND USES. Rhubarb is stomachic, tonic, mildly 

 cathartic, and afterwards astringent. SmaU and repeated 

 doses improve the appetite, correct slight gastric derange- 

 ment ; in virtue of their tannin may even diminish secretion 

 and peristalsis ; by their ehrysophanie acid impart to the 

 faeces a yellow-brown hue, and may be detected in the 

 blood, urine, and occasionally in the milk. Larger doses, 

 in dogs and cats, as in human patients, are mild cathartics, 

 stimulate the peristaltic movements, especially of the 

 stomach and small intestine, and are said to increase 

 secretion of bile. Even small doses, insufficient to purge 

 fasting dogs, slightly increase all the constituents of bile 

 (W. Rutherford). In horses and cattle rhubarb has scarcely 

 any purgative effect ; a pound has been given to cattle 

 without moving the bowels, while half a pound to a poum 



