352 RUBIACE^. 



Description — (A.) Of Cinchona Barks generally — In the develop- 

 ment of their bark, the various species of Cinchona exhibit considerable 

 diversity. Many are distinguished from an early stage by an abundant 

 exfoliation of the outer surface, while in others this takes place to a 

 smaller degree, or only as the bark becomes old. The external appear- 

 ance of the bark varies therefore very much, by reason of the greater 

 or less development of the suberous coat. The barks of young stems 

 and branches have a greyish tint more or less intense, while the outer 

 bark of old wood displays the more characteristic shades of brown or 

 red, especially after removal of the corky layers. 



In the living bark, these colours are very pale, and only acquire their 

 final hue by exposure to the air, and drying. Some of them however are 

 characteristic of individual species, or at least of certain groups, so that 

 the distinctions originated by the bark-collectors of 'pale, yellow, red, 

 etc.* and adopted by druggists, are not without reason. 



In texture, the barks vary in an important manner by reason of 

 diversity in anatomical structure. Their fracture especially depends 

 upon the number, size, and arrangement of the liber fibres, as will be 

 shown in our description of their microscopic characters. 



The taste in all species is bitter and disagreeable, and in some there 

 is in addition a decided astringency. Most species have no marked 

 odour, at least in the dried state. But this is not the case in that of G. 

 officinalis, the smell of which is characteristic. 



(B.) Of the Barks used in pharmacy — For pharmaceutical pre- 

 parations as distinguished from the pure alkaloids and their salts, the 

 Cinchona barks employed are chiefly of three kinds. 



1. Pale Cinchona Bark, Loxa Bark, Croiun Bark"^ — This bark, which 

 previous to the use of Quinine and for long afterwards, was the ordinary 

 Perwoian Bark of English medicine, is only found in the form of quills, 

 which are occasionally as much as a foot in length, but are more often 

 only a few inches or are reduced to still smaller fragments. The quills 

 are from f down to an |^ of an inch in diameter, often double, and 

 variously twisted and shrunken. The thinnest bark is scarcely stouter 

 than writing paper ; the thickest may be tV of ^^ inch or more.^ The 

 pieces have a blackish brown or dark greyish external surface, variously 

 blotched with silver-grey, and often beset with large and beautiful 

 lichens. The surface of some of the quills is longitudinally wrinkled 

 and moderately smooth ; but in the majority it is distinctly marked by 

 transverse cracks, and is rough and harsh to the touch. The inner side 

 is closely striated and of a bright yellowish brown. 



The bark breaks easily with a fracture which exhibits very short 

 fibres on the inner side. It has a well-marked odour sui generis, and 

 an astringent bitter taste. Though chiefly afforded by C. o^cinalis, 

 some other species occasionally contribute to furnish the Loxa Bark of 

 commerce as shown in the conspectus at p. 355. 



^ The following are common terms in re- sort of Loxa Bark, shipped for the use of 

 ference to the barks of Peru : — Amarilla the royal family of Spain, 

 (yellow), hlanca (white), Colorado or roja * In the old collections of the Royal Col- 

 ored), naranjada (orange), negrilla lege of Physicians, there are specimens of 

 (brovm), very thick Loxa Bark, of a quality quite 



" Cortex Cinchonce pallidce ; F. Quinquina unknown there at the present day. They 



Loxa; G. Loxachina. The term Croiwre are doubtless the produce of ancient trees, 



Barh was originally restricted to a superior such as were noticed by La Condamine. 



