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Show 116 COMMON PERUVIAN BARK TREE. The bark which comes from Guanacoconsists of much thicker, coarser, and flatter pieces; externally of a dark brownor almost black colour, but internally it has the same cinnamonco. lour; and in its resinous fracture, smell, and taste, it exactly resembles the former. When genuine, both varieties are excel. lent remedies, although the formerbe generally preferred on the continent andthe latter in Britain. 2. Yellow Peruvian bark. ‘This variety of bark has only been introduced into European practice since 1790, whenit was sent from Santa Fé by Mutis. It is the bark of his Cin. chonalatifolia, under which he includes the nitida, glabra, or lanceolata, fusca, or rosea, angustifolia, or tunita, the officinalis of Condamine and Vahl. It consists of pieces about six inches in length, thicker, and less rolled up, than the commonbark. Its internal surface is of a deeper red. It sometimes wants the epidermis, which is often as thick as the barkitself. It is lighter and morefriable than the former variety; its fractureis fibrous; and when reduced to powder, its colour is paler. Its taste is much more bitter, astringent, and stronger, but its smell is weaker.» Its decoction when hot is redder, but when cold, paler. Its solution strikes a deeper colour with sulphate of iron, It contains more of the active constituents than either of the others, but less gum than the common, and less resin than the red. It is much more powerful than the preceding species, and, according to Mutis, is the only one which is directly febrifuge, The epidermis should always be removed before it be powdered. 3. Red Peruvian bark is obtained from the Cinchona magnifolia of Ruiz and Pavon, the oblongifolia of Mutis. 1t occurs generally in muchlarger, thicker, flatter pieces, but sometimes also in the form of quills. It is heavy, firm, sound, anddry; friable between the teeth; does not Separate into fibres; and breaks, not shivery, but short, close, and smooth. It has three layers: the outer is thin, rugged, of a reddish brown colour, but frequently covered with mossy matter; the middle is thicker, more compact, darker coloured, very resinous, brittle, and yields first to the pestle: the inmost is more woody, fibrous, and of a brighter red. Its powder is reddish, like that of Armenian bole. Its astringency and bitterness are more intense, andit contains moreresin than the pale bark. It is not, however, allowed by COMMON PERUVIAN BARK TREE. 117 Mutis to be like the yellow bark, directly febrifage. It is said to be more frequently adulterated. The great price of cinchona bark has sometimes tempte d dis. honest mento adulterate it with other similar and less powerf ul barks, and, what is still mure blameable, with genuin e bark, from which the active constituents have been entirel y extracted by decoction with water, Inselecting cinchona bark, we must therefore take care,that, besides the. characteristics already noticed, it be dense, heavy, and dry, not musty or spoiled by moisture, and that a decoction made of it have a reddish colour when warm, but when cold become paler, and deposit a brownish red sedime nt. Those pieces whose taste is simply intensely bitter, or very astringent, or nauseous, or merely mucilaginous, whose surfac e is smooth or polished, of a dark colour, or pale yellow, or red, which are tough or spongy, whose barkis fibrous, woody, or powdery, and their internal colour white or gray, are to be rejected. There are few vegetable substances which have been subjected to analysis more frequently, and by abler chemists, than the cinchona bark. But from the difficulty of the subject, and from essential differences in the chemical propert ies of several varieties confounded under one denomination, contra dictory ree sults have arisen, and our knowledge of the subject is still im- perfect, Vauquelin has lately done much to lessen this confu- sioit, by showing that there are three, if not four, classes of cmchona bark, differing essentially in chemical constitution; but unfortunately he has not been able to designate with bos tanical accuracy the individuals he found to belong to each, The first class precipitate astringents, but not gelatine, The second precipitate gelatine, but not astringents. The third precipitate both astringents andge latine; and, Lastly, some barks confounded with these precipitate neither astri ngent nor gelatine; but these Vauquelin, Viewing the genus chemically, does not consider as cinchonas. Individuals in each of the three first classes are capable of curing intermittents, which shows howinsufficient our analysis, in its present state » is from explaining the connexion between the medical virtues and chemic al properties of this remarkable seuus. Besides tt tese principal difierences, on which Vauquelin founds his classifi cation, cinchona barks vary in the effects of any chemical agents. ‘The infusions of some kinds redden |