Dr. Duncan, jun., supposed that the precipitate formed with infusion of galls was a peculiar vegetable principle, and named it Cinchonin : and Dr. Gomez of Portugal afterwards verified this supposition by procuring it in crystals, by acting upon the aqueous infusion and the alcoholic extract of pale bark, with Liq. Potassae; he regarded it as analogous to resin. Lau-bert also, who procured it by another process, regarded it as white resin. Fabroni conceived that he was authorised in concluding from his experiments, that "the febrifuge virtue does not belong essentially and individually to the astringent, the bitter, or any other soluble principle, as the quantity of these increases by long boiling, while the virtues of the decoction decrease. He also contended that the febrifuge virtue does not reside in that principle which destroys the emetic property of tartarized antimony, and precipitates iron, since the decoction contains more of it than the infusion, while its virtues are evidently less."2 It was concluded from these doubts, and many others that had been raised, that much was yet to be done before the principle of cinchonas effective in the cure of fevers could be ascertained, and time has displayed the truth of this opinion.3

1 He examined seventeen different kinds, but was not able to ascertain the names of the trees from which they were obtained.

2 The effect of this principle was first noticed by Dr. Maton; and soon after by Seguin, who immediately concluded that it was gelatine; but this opinion was . proved to be erroneous by Dr. Duncan, jun., who found that it was a principle sui generis, and named it cinchonin. Vide Nicholson's Journal, vii. 226.

The analyses of the cinchona barks which first developed their active principles are those of MM. Pelletier and Caven-tou. The following are the components of the three officinal species :-1. In pale hark, and also in all the species, is found, first, kinic acid, combined with the cinchonia, forming an acidulous kinale of cinchona; second, a green fatty matter, first detected by Laubert; third, a red, nearly insoluble colouring matter, which is termed red cinchonic, discovered by Reuss; fourth, tannin; fifth, a yellow colouring matter, detected by Laubert; sixth, kinate of lime; seventh, gum; eighth, starch; and ninth, woody fibre. 2. In yellow bark, the acid is combined with quina, and a small proportion of cinchonia. That former alkaline base was found to be very soluble in ether, and to form salts with the acids different from those formed by cinchonia. The components of yellow bark are, acidulous kinates of quina and cinchonia, a deep yellow fatty matter, red cinchonic, tannin, yellow colouring matter, kinate of lime, starch, and woody fibre. 3. Red bark contains acidulous kinates of cinchonia and of quina in a large quantity, reddish fatty matter, red cinchonic, tannin, kinate of lime, yellow colouring matter, starch, and woody fibre.

1 Annates de Chimie, 1. c.

2 Edinburgh Medical and Surgical Review, ii. 338.

In consequence of a chymical theory of the mode in which cinchona acts on the living body, Fabroni made some curious experiments to ascertain the relative affinity of different cinchonas to oxygen. In imitating his experiments with the three officinal species, I found that, when half a drachm of each of these barks in powder was separately mixed with half a fluid ounce of strong nitric acid, in similar vessels, the temperature of the atmosphere at the time being 70°, and that of the acid 71°, in the space of four minutes, the heat produced raised the mercury in the thermometer as follows:

Common pale bark, - to 120°

---------- yellow bark, -to 123°

---------- red bark, -to 119°

The mixture in each vessel was gradually swollen as the heat increased, and nitrous fumes were given out, showing the evident decomposition of the acid.

According to my own experiments, the following are the known constituents of the officinal cinchonas: Cinchonia or quina 1, according to the species of bark analysed, united with the kinic acid2, kinate of lime, resin, red cinchonic, fecula, yellow colouring matter, gluten or ferment, volatile oil8, and tannin. I separated the resin in a pure state by evaporating the ethereal tincture on the surface of cold water; and the gluten, as Fabroni also found it, was separable by water, occasioning the spontaneous fermentation of the decoction and infusion in summer, and decomposible by fermentation. MM. Alibert and Cabal demonstrated the presence of iron in cinchona, by incinerating the bark, dissolving the ashes in nitric acid, and adding ferro-cyanate of potassa, which precipitated prus-sian blue.

The two alkaline bodies cinchonia and quina, found in these barks, unite readily with the acids, particularly the sulphuric; and their sulphates are now generally employed instead of entire barks or their other preparations.

The sulphate of cinchonia is so little employed, on account of the expense of preparing it, that I shall here describe its

1 The ultimate components of these alkaloids, according to Pelletier and Dumas, are: -

Annates de Chimie, lix. 1. c. The name of the acid is derived from kina kina, an old appellation of the bark. Dr. Duncan proposes to call it cinchonic acid, as the present name would lead to the supposition that it is procured from kino. 3 Dr. Irwin first obtained a small portion of this oil.

Characters and composition : it is obtained in the same way as ordered in the pharmacopoeia for preparing the sulphate of quina. It crystallizes in short white six-sided prisms, derived from an oblique rhomboidal prism. The prisms are often aggregate. They are soluble in 6.5 of alcohol of sp. gr. 85., and in 54 parts of water at a temperature of 60°; Fahr. According to M. Beaup's experiments, these crystals consist of cinchona 84.324, sulphuric acid 10.811, and water 4.865, or of one atom of cinchonia = 156.55,+one of acid = 40.1,+ four atoms of water = 36; making the equivalent 242.65.1 They effloresce in dry air. A disulphate is also formed less soluble than the sulphate.