246 BARKS 



and appears to be identical with rheum-emodin, but different from 

 aloe-emodin and senna- emodin. 



Frangula-emodin has been known under various names, viz. frangulin 

 (Casselmann, 1857), frangulinic acid (Faust, 1869, Keussler 1873), 

 avornic acid (Kubly, 1866), rhamnoxanthin (Binswanger, 1850). 



Frangulin is said not to be present in the fresh bark, but to be 

 produced from some unknown constituent during the maturing of 

 the bark, the change in the physiological action of the bark occurring 

 simultaneously. The bark also contains free frangula- emodin, chryso- 

 phanic acid and an iso- emodin. 



The total quantity of emodin present in the bark either free or in the 

 form of a rhamnoside has been estimated at 1 per cent, in old bark, 

 2 per cent, in bark of medium age, and 3*8 per cent, in very young 

 bark. This proportion is insufficient to account for the laxative 

 action of the drug, and the assumption is that either other, at present 

 unknown, purgative bodies are present or that the frangulin exists 

 in an unknown more active form. 



The presence of emodin in the bark is readily demonstrated by 

 moistening O'l gm. of the powdered bark with 10 drops of alcohol and 

 boiling for a few moments with 10 c.c. of water. The cooled decoction 

 is shaken with 10 c.c. of ether, the yellowish ethereal solution separated 

 and shaken with ammonia, which will acquire a reddish colour. 



Uses. Alder buckthorn bark has been used as an agreeable laxative, 

 preferable to cascara sagrada on account of its less disagreeable taste. 



Substitutes. The bark of R. carniolicus, Kerner, is not unfrequently 

 substituted for that of R. Frangula ; the cork contains a dull red, 

 not crimson, colouring matter ; medullary rays 4 to 7 instead of 2 

 to 3 cells wide ; outer bark, when formed, contains groups of scleren- 

 chymatous cells. 



The bark of Alnus glutinosa, Gaertner (N.O. Betulacece) exhibits 

 in transverse section a ring of sclerenchymatous cells. The bark of 

 R. catharticus, Linne, is glossy reddish brown and has very distant 

 lenticels. 



CASCARA SAGRADA 



(Cortex Rhamni Purshiani, Sacred Bark, 

 Chittem Bark) 



Source, &C. Cascara sagrada is the bark of Rhamnus Purshianus, 

 de Candolle (N.O. Rhamnece), a shrub or small tree abundant in North 

 California and in the States of Washington and Oregon, the bark 

 being collected in these States and exported from San Francisco. 

 The bark of R. calif ornicus, Eschscholz, was known to the Spanish 

 settlers in California as cascara sagrada, a name which has since 



