We Shall Here Confine Ourselves To This Observation, That, In The Species Of The Genus Cinchona, The Antifebrile Virtues Do

Not appear to belong to the tannin (which is only accidentally mingled in them), or to the cinchonate of lime;

But in a resiniform matter, soluble both by alcohol and by water, and which, it is believed, is composed of two principles, the cinchonic bitter and the cinchonic red.* (* In French, l'amer et le rouge cinchoniques.) May it then be admitted, that this resiniform matter, which possesses different degrees of energy according to the combinations by which it is modified, is found in all febrifuge substances? Those by which the sulphate of iron is precipitated of a green colour, like the real cinchona, the bark of the white willow, and the horned perisperm of the coffee-tree, do not on this account denote identity of chemical composition;* and that identity might even exist, without our concluding that the medical virtues were analogous. (* The cuspare bark (Cort. Angosturae) yields with iron a yellow precipitate; yet it is employed on the banks of the Orinoco, and particularly at the town of St. Thomas of Angostura, as an excellent cinchona; and on the other hand, the bark of the common cherry tree, which has scarcely any febrifuge quality, yields a green precipitate like the real cinchonas. Notwithstanding the extreme imperfection of vegetable chemistry, the experiments already made on cinchonas sufficiently show, that to judge of the febrifuge virtues of a bark, we must not attach too much importance either to the principle which turns to green the oxides of iron, or to the tannin, or to the matter which precipitates infusions of tan.) We see that specimens of sugar and tannin extracted from plants, not of the same family, present numerous differences:

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