This bark yields quinine, much quinidine, also some cinchonine.

Cinchona lancifolia grows at a great elevation in the forests near Bogota, in New Granada, and is now known as Cinchona condaminea (var. δ lancifolia.)

Cinchona cinerea, silver, grey, or Huanuco Bark formerly officinal in the Edinburgh and Dublin Pharmacopoeias, is the produce of Cinchona micrantha and Cinchona nitida; it occurs in quills, which are in general larger and coarser than those of the Brown bark; with a greyish epidermis, less wrinkled longitudinally and less completely cracked transversely; the smaller quills are often twisted spirally; and on the inner surface the bark is more uneven, and of a redder colour than Loxa or Brown bark. The produce of Cinchona nitida and Cinchona micrantha are usually mixed together; that from the former tree is superior. These trees grow in the forests of Cuchero and Huanuco in northern Peru. The barks are rich in quinine, quinidine, and cinchonine.

For the description of other cinchona barks used in commerce for the extraction of the alkaloids, the reader is referred to more extended works on the subject, especially to the article cinchona, the last effort of the late Dr. Pereira and Howard's illustrations.

Prop. & Comp. The different barks are closely allied to each other in composition: they all contain acid and alkaline principles peculiar to the genus Cinchona, together with other matters common to many kinds of barks. The acids of the cinchona barks are as follows:

Quinic or Kinic Acid (2 HO, C28 H20 O20) can be crystallized in oblique rhombic prisms, resembling tartaric acid in appearance; soluble in water, and acid in taste; less soluble in alcohol, and very sparingly soluble in ether; it yields a yellow, crystallizable pungent, sublimate, kinone (C12 H4 O4) when distilled with some oxidizing agents.

Cincho-tannic Acid (C28 H19 O17 ?) differs from ordinary tannin or tannic acid, in precipitating the persalts of iron, green, and rapidly absorbing oxygen, especially when united with an alkali.

Red Cinchonic supposed to be produced by the oxidation of cincho-tannic acid; a red substance, hence its name; almost insoluble in water, but soluble in alcohol, ether, alkalies, and acids; the solutions have a deep red colour.

Kinovic Acid found in many kinds of barks; in its chemical characters it somewhat resembles stearic acid; its solutions precipitate copper green, a reaction employed as a test of its presence.

Quinia or Quinine (C40 H24 N2 O4), or with 6 equivalents of water when crystallized, the most important alkaloid contained in the barks, exists in the largest quantities in Calisaya bark; when pure, it is white, crystallizing with some difficulty as the hydrate; soluble in about 350 parts of cold water, 60 parts of ether, and very soluble in alcohol; fuses, when heated, into a resinous mass; forms salts with acids, and its solutions exhibit a fluorescent appearance, and when treated with excess of chlorine water and ammonia afterwards added, a dark emerald-green liquid is produced. Quinia forms crystallizable salts with acids; the best known is the officinal salt, Quiniae Sulphas or sulphate of Quinine.

Cinchonia or Cinchonine (C40 H24 N2 O2), an alkaloid contained chiefly in the pale varieties of bark, it readily crystallizes from its alcoholic solution in brilliant colourless four-sided prisms; it is almost insoluble in water and ether, and requires about 30 parts of rectified spirit to dissolve it; unites with acids, and forms soluble salts, the solutions of which are not fluorescent, and do not give the green colour with chlorine and ammonia, but merely become light brownish-yellow.

Quinidina or Quinidine, a third alkaloid, contained in many of the cinchona barks, especially in those of New Granada, and isomeric with quinine (C40 H24 N2 O4), with 4 equivalents of water when crystallized, occurs, when pure, in white prisms, readily crystallizing from alcohol, and also when precipitated from the watery solutions of its salts, by means of an alkali; it is very bitter, but les3 intensely so than quinia, and its solutions are fluorescent: it is much less soluble in water than quinia, and less soluble in ether, and its sulphate is also much more soluble than that of quinia, much less so than that of cinchonia. The solutions of quini-dine, when treated with chlorine water and ammonia, show the emerald-green appearance, as in the case of quinine.

Cinchonidina or Cinchonidine ,(C40 H24 N2 O2), a fourth alkaloid, found in cinchona barks, and isomeric with cinchonine, occurs in hard, brilliant, striated, rhomboidal prisms, which are anhydrous, and insoluble in ether; it forms crystallizable salts, the solutions are fluorescent, but when treated with chlorine water, and subsequently with ammonia, do not give rise to the emerald-green colour.

M. Pasteur, from an examination of quinine, quinidine, cin-chonine, and cinchonidine, finds that quinine, by being carefully heated in the form of a salt, as the tartrate, is changed into an isomeric body, quinicine, and cinchonine, under like circumstances, into cinchonicine, substances similar to them, but amorphous; and he also finds that quinidine and cinchonidine are converted into the same isomeric substances, quinicine and cin-chonicine. According to Pasteur, quinine and quinidine strike green with chlorine and ammonia, but cinchonine or cinchonidine do not and the alkaloid, usually designated quinidine commonly, consists chiefly of cinchonidine.

The following are the relations in which the four alkaloids and their isomeric modifications stand in regard to their action upon polarized light.

Quinine turns the plane of polarization powerfully to the left hand.

Cinchonidine " " " "

Cinchonine turns the plane of polarization strongly to the right hand. Quinidine " " " "

Both quinicine and cinchonicine turn the plane of polarization feebly to the right hand.