366 SUBTERRANEAN ORGANS 



rhubarb yields from 7 to 13 per cent. (B.P. not more than 15). English rha- 

 pontic rhubarb yields usually less than Chinese. It occurs in very large cluster 

 crystals, and is the cause of the gritty taste of the drug. 



Uses. In small doses rhubarb is a bitter stomachic and intestinal 

 astringent ; in larger doses it causes purgation, which is followed by 

 an astringent effect due to the tannoid constituents. It is given in 

 cases of indigestion with diarrhoea and as a mild laxative. 



FIG. 192. Chinese Rhubarb (flat High-dried). 

 Slightly reduced. 



Varieties. Three varieties of Chinese rhubarb are recognised on 

 the market, viz. Shensi, Canton, and High-dried, each of which may 

 occur in ' flats ' or ' rounds.' 



Shensi Rhubarb is characterised by its very compact nature, bright 

 yellow coat, distinct whitish reticulations, and * nutmeg ' fracture 

 (fig. 189) : the odour is agreeable and free from marked empyreuma, 

 the taste slightly bitter. That which exhibits a bright pink fracture 

 is preferred. 



Canton Rhubarb may be distinguished from Shensi by the fracture, 



