156 rOLYOONACHJ^. 



^emg 



Himalayan rhubarb^ states that it is only an inferior variety 

 tbat reaches the plains of Hindustan, He tested the action of 

 the fresh root, and found it to resemble the action of Russian 

 rhubarb. {Op. cit.y p. 188.) 



Description. — China rhubarb consists of portions of a mas- 

 sive root which display considerable diversity of f orm^ arising from 

 the various operations of paring, slicing and trimming to which 

 they have been subjected. Thus some pieces are cylindrical or 

 rather barrel-shaped, others conical, while a large proportion 

 are plano-convex, and others again arc of no regular shape. 

 These forms are not all found in the same package, the drug 



usually sorted into round and flat rhubarh. - The pieces 

 are from 3 to 4 inches long by 2 to 3 inches in breadth. 

 Many pieces are pierced with a hole. The drug is dusted over 

 with a bright brownish-yellow powder, on removal of which the 

 surface is seen to have a rusty-brown hue. The chai^acter which 

 most readily distinguishes the rhubarb of China is that well- 

 developed pieces, broken transversely, display dark lines arranged 

 as an internal ring of star-like spots. In good rhubarb the 

 interior is compact and veined with reddish-brown and white, 

 sometimes mixed with iron-grey. The root when chewed tastes 

 gritty, by reason of the crystals it contains of oxalate of calcium ; 

 but it is, besides, bitter, astringent and nauseous. The odour is 

 peculiar. [Phannacogmphia,) The characters of the Chinese 

 stick rhubarh which is used in India have already been noticed ; 

 it would appear to consist of the smaller branches of the root 

 which have been removed in preparing the drug for European 

 commerce. 



Chemiaal composition. --T]xe purgative principle of rhubarb is 

 Cathartic ^ceV/, a glucoside discovered by Kubly {Bull Soc. Chim. 

 Fari$, 1866) in Senna in combination with calcium and magne- 

 Buira, and now known to be present in many other purgative 

 drugs. Rhubarb also contains Ghrysophanic acid, CH^'^O*, andan 

 allied substance Emodiu, C**H^"0' ; a tannin, C^^H^'O^*, named 



Rheo-tannicaeidby Ivubly; resins and muclbiginous matters- 

 Small auantities of albuminoul anKQiuTi^A.^ ^...i- . «„:j ^^4- ..nrl 



