The flat Yellow Bark, or that in splints, occurs either with the epi dermis, or divested of it (China regia nude). Pieces retaining the epidermis are generally from one to five inches broad, generally quite flat, but sometimes slightly curved, from three to fifteen indica long, and from one quarter to three-quarters of an inch thick. The charac ters of the epidermis correspond with that above described : the uncoated kind is most frequent, and occur* in splints from one to eight lines thick. The colour varies, but is generally a reddish or rusty-brown, and Is nearly the same on both surfaces, so that in pieces which have become convex on the inner side, and concave on the outer, as often happens, it is difficult to determine which was the exterior ; this is by far the best kind of yellow bark.
Adulteration of Yellow Bark is not very easy, but a kind of humalia like bark used to be substituted for it.
The odour of genuine Yellow Bark is slightly that of tan. The taste is faintly acid, strongly but not unpleasantly bitter, aromatic, stimu lating, and slightly astringent.
The analyses of uncoated Yellow Bark (Calisaya) by Pelletier and Caventou show its composition to be super-kinate of quinia, fatty matter, slightly soluble red colouring-matter (red cinchonic acid), soluble red colouring-matter (more than in gray bark), tannin, kinate of lime, lignin, amylum. When the uncoated kind is analysed, some Cinchonia is obtained. By a comparative analysis it is found that a pound of flat uncoated yellow bark yields nearly twice as much Quinia as the quilled sort, a point of much importance to the pre parers of that alkaloid_ The Carthagena yellow barks both contain Quinia, but in less quantity than the Calisaya bark ; the hard Carthagena bark, in addition, yields Cinchonia, but not the fibrous kind.
The Red Bark, of which one kind only is known in English trade, is generally referred to C. oblongifolia ; though many doubts may be held on this head. Bergen is much more disposed to consider the C. obloegifolia as the source of the China Nova, or Surinam bark, which is not officinal in Britain ; this also is doubtful. Red bark has been known for 130 years, but was not much used in Europe till 1779. It occurs in quills and flat pieces, most frequently in the latter form. The quills are rolled singly, or doubly, from 4 to 15, but generally from 4 to 6 inches long, and from a few lines to I inch in diameter, the bark being from 1 to 4 lines thick. The figure of
the flat pieces is variable, being generally very much broken, fre quently with the epidermis entire ; but this is often partially, seldom or never completely, absent. The length. is generally from 4 to 24 inches, the thickness from I to I inch, and the breadth 1 to 3 inches. The quills most frequently have the epidermis entire ; some of them have a whitish-yellow, or grayish-white epidermis (interrupted by longitudinal and irregularly transverse cracks), a red hue shining through it. In fact, even in pieces with the epidermis entire, and covered with many lichens, the red hue is seen ever shining through characteristic mark of this kind of bark. The flat pieces have generally an amazing number of lichens upon them. In these pieces also what is called the rete mucosum is often very spongy. Warty bodies are found on some varieties. The inner surface is a reddish brown, varying in intensity. The fracture iu thin quills is smooth, in those of a moderate thickness fibrous, and in thick quills and flat pieces fibrous and splintery : the epidermis, when penetrated by the resinous principle, exhibits a vitreous shining ring.
Pelletier and Caventou analysed a specimen of the variety free from warts, and found it to contain Superkinate of Quinia large quantity.
Superkinate of Cinchonia Slightly soluble red colouring-matter, or red Cinchonic Acid.
Soluble red colouring-matter (tannin).
Yellow colouring-matter ; fatty matter.
Kinate of Lime. Woody Fibre. Starch.
The relative proportions of Quinia and Cinchonia differ in different specimens ; a pound of bark yielding in some instances 70 grains of Cinchonia and 77 grains of sulphate of quinia, in others 184 grains of Cinchonia and only 9 grains of sulphate of quinia.
Tile Humalies, or Brown Bark, is not known in English commerce ; its source is not accurately determined.
Several inferior kinds, and others erroneously reputed to he Cinchona barks, are met with, either accidentally or fraudulently mixed with or passed fur the genuine ; but they may be known by not possessing the characters of the best kinds as given above.
Dr. Lindley, in his ' Flora 31edica,' gives the following as the result of his inquiries with regard to the barks used in medicine :— - - L lacer, u.