CORTEX CINCHON.E. 357 



posed by caustic lye, and the alkaloids set at liberty assume the 

 crystallized state. This is in our opinion the origin of the crystals 

 under notice. 



The greater number of the parenchymatous cells are loaded with 

 small starch granules, or in young and fresh barks with chlorophyll 

 In several barks, as in that of G. lancifolia Mutis, numerous cells of 

 the middle cortical layer and even of the medullary rays, are provided 

 with somewhat thick waUs, and contain either a soft brown mass 

 or crystalline oxalate of calcium. These cells have therefore been 

 called resin-cells and crystal-cells ; they are mostly isolated, not forming 

 extensive groups or zones, and their walls are not strongly thickened as 

 in true sclerenchymatous tissue. If thin sections of the barks are 

 moistened with dilute alcoholic perchloride of iron, the walls of the cells, 

 except the fibres and the cork, assume a blackish-green due to cincho- 

 tannic acid ; this applies even to the starch granules. 



Characters of particula/r soii^. — The modifications of general struc- 

 ture just described, are sufficient to impart a special character to the 

 bark of many species of Cinchona, provided the bark is examined at 

 its full development, the structural peculiarities being far from well- 

 marked in yoimg barks. 



Thus it is not possible to point out any distinctive features for the 

 Loaxt Bark of commerce, because it is mostly taken from young wood. 

 We may say of it, that neither resin-cells nor crystal-cells occur in its 

 middle layer, that its laticiferous vessels become soon obliterated, and 

 have indeed disappeared in the older quills ; and that the liber-fibres 

 form interrupted, not very regular, radial rows. 



The quills of G. Galisaya display large laticiferous ducts, which are 

 wanting in the flat bark. There is a peculiar sort of the latter called 

 Bolivian Galisaya. (already mentioned at p. 353), the flat pieces of which 

 still possess very obvious laticiferous vessels. As to the liber-fibres of 

 Calisaya bark, they are, as before stated (p. 356), scattered throughout 

 the parenchymatous tissue or endophlceum. In the bark of G. scrobicu- 

 la.ta, which might at first sight be confounded with Calisaya bark, the 

 liber-fibres form radial, less interrupted rows. The microscope affords 

 therefore the means of distinguishing these two barks. 



The barks of G. succirubra are particularly rich in laticiferous ducts, 

 mostly of considerable diameter, in which the formation of new paren- 

 chyme may not unfrequently be observed. The orange liber-fibres oc- 

 curring in this bark are less numerous, more scattered, and of smaller 

 size than in Calisaya. The fracture of Red Bark, especially the flat sort, 

 is therefore moi'e finely granular and not so coarse as that of Calisaya. 



The structural characters of Cinchona barks may lastly be fully ap- 

 preciated by examining barks of the allied genera Buena, Cascurilla and 

 Ladenbergia, which were formerly known under the name of False 

 Cinchona Barks. The microscope shows that the liber-fibres of the 

 latter are soft, branched and long, densely packed into large bundles, 

 imparting therefore a weU-marked fibrous structure. The external 

 appearance of these barks is widely different from that of true cinchona 

 barks ; none of them it would appear is now collected for the purpose 

 of adulteration. 



Chemical Composition — Themost important and at the same time 



