276 BARKS 



to the air for some time, glistening prismatic crystals can be observed 

 even with the naked eye. 



The section is very characteristic. The outer layer, a thin brownish 

 cork, encloses a narrow brown cortex separated by a distinct paler 

 line (of sclerenchymatous cells) from the very thick bast which in 

 older barks constitutes nine-tenths of the drug. This bast contains 

 an abundance of sclerenchymatous tissue arranged in rounded or 

 tangentially elongated groups. The section resembles that of sassy 

 bark, but the groups of sclerenchymatous cells are much smaller, and 

 the colour is reddish brown. 



The drug has a very characteristic odour and a pungent taste. 



The student should observe 







(a) The brownish cork and brown striated inner surface, 



(b) The characteristic transverse section, and 



(c) The distinctive odour ; 



and should compare this bark with 



(i) Sassy bark, which has a nearly black inner surface, darker 

 outer surface, and fewer and larger groups of sclerenchy- 

 matous cells ; 



(ii) Bebeeru bark, which is smoother and exhibits distinct 

 medullary rays, but very inconspicuous masses of 

 sclerenchyma ; 



(iii) Flat red cinchona bark, which is characterised by its rusty 

 red colour, reddish warts, and bitter astringent taste. 



Constituents. Paracoto bark contains several crystalline bodies, 

 the chief of which, paracotoin, C 12 H 8 O 4 , occurs in pale yellow scales 

 melting at 152, and give a yellowish brown colour with nitric acid ; 

 it is dioxymethylenephenylcumalin. Other crystalline bodies present 

 in the bark are phenylcumalin (leucotin), hydrocotoin (dimethyl ether 

 of benzoylphloroglucinol) , methylhydrocotoin, protocotoin (dioxy- 

 methylene-phloroglucinol) , and methylprotocotoin (oxyleucotin) . 



The bark also contains piperonylic acid, resin, tannin, and a little 

 volatile oil. 



Uses. The drug has been employed with success for diarrhoea, but 

 is not much used now. 



Varieties. True coto bark closely resembles paracoto ; it is said 

 to be distinguished by its odour, which recalls cinnamon, that of 

 paracoto recalling nutmeg, and by its taste, which is more pungent. 

 The most definite distinctive characters lie in the constituents. True 

 coto contains cotoin and phenylcumalin, the substance formerly 

 known as dicotoin being probably a mixture of these two substances. 

 Cotoin, C 4 H 12 4 , is the monomethyl ether of benzoylphloroglucinol ; 





