No very well marked difference in the action of the different barks has yet been established: there can be no doubt, however, that their effects depend on the alkaloids contained in them, and consequently any peculiarity of the bark would be that of the prevailing alkaloid.

As a rule, quinia exists in large quantities in yellow bark, cinchona in pale barks, and the red bark is stated to contain about equal amounts of the two alkaloids. Quinidine and cinchonidine are more especially found in the Carthagena barks. According to the results of recent examinations, collected in the form of a table by the late Dr. Pereira,

Yellow or Calisaya barks yield from 2.5 to 3.8 per cent. of quinine;

Pale or Loxa barks, from about 0.7 to 1.4 per cent. of alkaloids chiefly cinchonine or quinidine, with a little quinine;

Best red barks, 2.6 per cent. of quinine, and 1.5 per cent. of cinchonine;

Gray or Huanuco barks, from 1.7 to 2.1 per cent. of alkaloids, chiefly consisting of cinchonine and quinidine, with occasionally some quinine.

Dose. Of any cinchona bark, in powder, 10 gr. to 60 gr.; of the decoction 1 fl. oz. to 2 fl. oz.; of the infusions, 1 fl. oz. to 2 fl. oz.; of the liquid extract of yellow cinchona, 10 min. to 1 fl. drm; of the tinctures (simple or compound), 1 fl. drm. to 2 fl. drm.; of sulphate of quinine, 1 gr. to 10 gr., or even 20 gr.; of compound tincture of quinine, 1 drm. to 2 drm.; of sulphate of cinchonine, 1 gr. to 10 gr.; of sulphate of quinidine 1 gr. to 20 gr.; of sulphate of cinchonidine, 1 gr. to 10 gr.; of hydrochlorate of cinchonine 1 gr. to 10 gr.

In intermittents, or when the dose of bark is required to be large, the salts of quinia or cinchonia are preferred; powdered bark was formerly given in such cases, but it is apt to disagree with the stomach, and cause nausea and vomiting; the liquid extract might be made use of, but their strength is by no means equivalent to the amount of bark made use of in their preparation, and the same holds good of all the pharmaceutic preparations made with water, the solvent powers of that fluid being unequal to abstract all the principles from the bark.

Adulteration of Cinchona Barks. Inferior non-officinal cinchona barks may be substituted for the officinal, and barks of other species may be sold for those of the genus cinchona; these are distinguished by their physical characters, and by finding the presence and amount of the cinchona alkaloids contained in them. The structure of the bark also affords some test of its value, for it has been found that the bark which exhibits when fractured a homogeneous texture, with a large amount of short fusiform ligneous fibres, uniformly distributed in the cellular tissue, contains a large amount of quinine; this is the character of true Calisaya barks. Barks rich in quinine generally contain much lime, and the strong infusions are precipitated by sulphate of soda; which is not the case with the barks yielding cinchonine. The same holds good with regard to the amount of tannin. Many methods of ascertaining the per-centage of alkaloids have been proposed; the following is the method given in the Pharmacopoeia for the examination of yellow cinchona bark: - One hundred grains of the bark are reduced to powder and thoroughly exhausted by maceration and percolation, with water acidulated with hydrochloric acid. To this solution, subacctate of lead is added until all the colouring matter is removed, care being taken to keep the fluid acid. The precipitate is removed by nitration, and to the filtrate caustic potash, enough to redissolve the precipitate which is at first formed, is added, and the solution then well shaken with successive quantities of ether, until a drop of the ether evaporated to dryness yields no perceptible residue. The ethereal solutions are then evaporated to dryness, and the residue, which consists of nearly pure quinia and should be readily soluble in dilute sulphuric acid, is weighed. Pale and red barks are tested in a similar manner, with the substitution of chloroform for ether in the process.

Of Sulphate of Quinine. On account of the high price of this salt, many adulterations have been practised. Sulphates of cincho-nine, quinidine, and cinchonidine, salicine, sugar of milk, cane sugar, mannite, starch, and stearic acid, form the most frequent organic adulterations; and sulphate of lime, precipitated to imitate the quinia salt, chalk, magnesia, and boracic acid, are among the most frequent inorganic additions. These latter, with the exception of boracic acid, are readily detected by their not dissolving in alcohol, and by heating the suspected salt on a piece of platinum foil, where they leave an ash, the nature of which can be ascertained by the ordinary tests: the organic impurities are more difficult of detection; cinchonine, cinchonidine and quinine can be discovered by their different solubilities in water, alcohol, and ether; salicine, by the blood-red colour produced by sulphuric acid; the sugars, by the solution of the salt, after the precipitation of the alkaloids by means of an alkali, being sweet; starch, by its striking blue with iodine; and stearic acid, by not dissolving in dilute acids. Boracic acid, if present, gives to its alcoholic solution the property of imparting a green tinge to flame. The British Pharmacopoeia gives the following quantitative test: - Ten grains with ten minims of diluted sulphuric acid and half a fluid ounce of water form a perfect solution, from which ammonia throws down a white precipitate. This redissolves on agitating the whole with half a fluid ounce of pure ether, without the production of any crystalline matter floating on the lower of the two strata, into which the agitated fluid separates on rest. The upper stratum of fluid, if entirely removed by a pipette and evaporated leaves a white residue, which, when dried in the air without heat, weighs 8.6 grains.

Ipecacuanha. Ipecacuan or Ipecacuanha. The dried root Cephaelis ipecacuanha; Lin. Syst., Pentandria monogynia; growing chiefly in the Brazils, and sent from Rio Janeiro.