CINCHONA, or, as it is commonly called, Peru vian Bark, is obtained from several species of the genus. Cinchona, which belongs to the class Pentandria, order Monogynia, and to the natural order Contort a Twenty five species have been described by the Spanish botanists as natives both of North and South America. Our ob servations, from the imperfect nature of the information which we possess, must be confined to the genus, and must not extend to the species. The cinchona is a tree which is found only in mountainous tracts, where it grows to the thickness of a man's body. The Spaniards have never yet attempted to cultivate it, but merely strip the natural trees of their bark ; a practice which must ulti mately destroy the genus, as they always die after being deprived of their bark. This operation is performed in the dry season, which is from September till November. The bark being well dried in the sun, is packed up in skins, so as to form bundles of one hundred, or one hun dred and fifty pounds weight. These packages are call ed Lcrdone by the Spaniards : they contain all the spe cies, which are afterwards sorted according to their qua lity.
Three kinds of bark are in use as a medicine in Eu rope. Of each of these we shall give a brief account, and afterwards conclude with a statement of the modes of preparation most commonly employed. The follow ing are the varieties enumerated by the Edinburgh Col lege.
1. Common bark.
2. Yellow bark.
3. Red bark.
1. common bark. Several varieties of this species of bark are brought to Europe ; the quilled variety from Loxa, and the fiat from Guanaxo, are the most remarka ble. The former of these comes over in pieces four or five inches long, rolled up very thin, externally of a grey ish brown, internally (when fresh broken) of a bright cinnamon colour. Its fracture is clean and even. Its taste is bitter and astringent, its smell peculiar but aromatic. The latter variety is imported in flat, coarse, and thick pieces ; and still farther differs from the quilled bark in having a much darker colour externally. In every other character it corresponds with the former. Both are said to be equally efficacious.
2. Yellow bark. This is less rolled than the quilled bark ; its pieces are also larger and thicker. It has a much deeper red colour. Its fracture is fibrous, and in powder it is much paler than in its entire state. Its taste is more powerful, though the smell is weaker, than the common bark. Its active principles are more abun dant. This hark has been only introduced into use since the year 1790, by Mutis, who considers it to be the on ly variety which possesses a real febrifuge quality.
2. Red bark. This variety is sometimes rolled, but more commonly is in flat, thick, large pieces. It is
heavy, firm, and dry. It has a smooth fracture. It is composed of three layers. When powdered, it has a red dish colour. It is more bitter and astringent than the common and yellow bark.
All the varieties of cinchona are highly valuable, and are consequently liable to be adulterated with various substances. It is therefore necessary to attend, in se lecting this drug, accurately to all of its characters.
Cinchona has long been known as a medicine in Peru, where the natives are said to have adopted its use from observing animals recur to it. Whatever may have been the source of its first employment; it was not tried by Europeans until the year 1640, when the Countess of Cinchon, the wife of the Spanish viceroy, was cured of the ague by means of it. It therefore derived its present name from her. It has also been called Jesuits bark, from the exertions made by these disciples of Loyola to introduce it. As it usually happens on the first appear ance of any novel remedy, considerable opposition was made to it by several eminent physicians ; but its effi cacy soon overcame the groundless clamour which had been excited.
Probably no vegetable substance has undergone so ma ny analyses, by the most distinguished chemists of Eu rope, as the different kinds of cinchona have been sub jected to, and yet little positive knowledge has been ob tained of its constituent parts. The following are the most important results that have been obtained respecting the composition of the different varieties of cinchona: To enter into a minute detail of the analysis of the individuals would far exceed our limits. The bases of all the vari eties is ligneous fibre, combined with which there are se veral other principles, which may be extracted by means of proper solvents. In all the varieties, they correspond, except in the proportion and consequent activity. A, cold infusion of common bark has a bitter taste and slight peculiar odour ; when a common heat has been employ ed, a larger quantity of the active principles is dissolved, hut the complete solution ceases, on cooling, as is indica ted by the turbidity of the fluid. A decoction of this bark has a very astringent taste, and a deep brown co lour. On cooling, its transparency is destroyed, and a precipitate is deposited, that is soluble in alcohol. Much heat destroys all the active principles of the bark by de composition. Alcohol, in all its modifications, is a pow erful solvent of the active principles of cinchona. A so lution of ammonia is also a powerful solvent of them. Vi• negar acts very imperfectly on them.