CINCHONA. 



475 



Cinchona, ish brown, internally (when fresh broken) of a bright 

 '*-~-f~me' 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 

 Lark ; 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 bark 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. 



3. 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 

 -ubstances. It is therefore necessary to attend, in se- 

 lecting this drug, accurately to all of its characters. 



Cinchona has been long 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 kito a minute detail of the analyses of the individuals 

 would far exceed our limits. The bases of all the vari. 

 t-tiw is ligneous jibre, 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, 

 but 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-iolTeut of the active principles of cinchona. A so- 

 ! ution of ammonia is also a powerful solvent of them. Vi- 

 negar acts very imperfectly on them. 



The agency of the different menstrua on the red and 

 yellow varieties of the cinchona, produces apparently the 



same results as on the cojnmon or pale bark, varying, Cinchoaj. 

 however, very considerably in degree ; the red being '*~~s~~* 

 more powerful than the common, and the yellow still 

 more so than the red. 



It is an object of considerable importance, as well as 

 of curiosity, to determine exactly the proportions in 

 which the different principles exist, in the varieties of 

 bark, as well as the relations which these principles have 

 to their efficacy as a medicine ; but, unfortunately, the 

 difficulties which are opposed to the analyses of such 

 fleeting and delicate substances, as the principles of vege- 

 tables, render this desire unavailing, at least in the pre- 

 sent state of science. The greater solidity of the princi- 

 ples of bark in hot water and in alcohol, would induce a 

 belief of its being a resin ; while, on the other hand, their 

 partial solidity in cold water, and their decomposition 

 even by a moderate degree of heat, are characteristic of 

 the extractive principle. 



The effects of chalybeates on the infusions f Peruvian 

 bark, indicate the presence of an astringent matter, which 

 seems to be intimately connected with the substance ex- 

 tracted by heated witer or by alcohol. The addition of 

 a solution of the sulphate of iron to the infusion, strikes 

 a dark olive green colour; a deeper shade oi the same co- 

 lour is produced by this salt in the decoction or tincture. 

 From this fact, it has been inferred, that tannin is pre- 

 sent, and, consequently, that a precipitate would be pro- 

 duced by a solution of gelatine. This effect, however, 

 is only induced in some varieties of the Peruvian bark ; 

 there being others, the infusions of which are not, in t 

 slightest degree, affected by the addition of gelatine, but 

 yield a precipitate on the addition of tannin. These sin- 

 gular phenomena have given rise to a very absurd hypo- 

 thesis of Seguin, in which h ascribes the agency of Pe- 

 ruvian bark to the presence of gelatine. 



Dr Duncan ascribes these effects to a mew ager.t, which, 

 he calls cinchonin. Vauquelin has made extended expe- 

 riments on the different species of cinchona, but they are 

 of less value than they would have been, had he detail- 

 ed the specific characters of each. Mr Murray has. 

 found, " that the watery infusion of the pale bark is not 

 sensibly precipitated either in gelatine or tanr.iu ; that of 

 the red bark is not precipitated by gelatine, but gives a 

 copious precipitate with tannin ; and that of the yellow 

 is rendered turbid by gelatine, and precipitated copious- 

 ly by tannin." It is vain to throw out conjectures, as 

 to the nature of this substance, until farther facts be 

 determined, on which we can rest with greater certain- 

 ty- 



Vauquelin has determined the presence of a peculiar 

 acid, to which he gives the name of Icinic acid, in some 

 varieties of the bark. 



The active principles of bark are rendered more solu- 

 ble in water by the acids, the alkalies, and some of the 

 earths, more especially magnesia. 



Much diversity of opinion prevails among medical men, 

 respecting the relative efficacy of the three kinds of bark 

 which we have enumerated. The red bark, when first 

 introduced into English practice, in consequence of a 

 Spanish vessel, freighted in part with it, being taken in 

 the year 1779, was tried in several of the London hospi. 

 tals, and was then, as is usual with every new remedy, 

 extolled to the skies ; but its reputation has given way 

 to that of the yellow bark, which is now generally con- 

 sidered to be most efficacious. 



The preparations of bark, which are admitted into 

 the British Pharmacopoeias, are, the decoction, the ear 

 tract, the infusion, the tincture, aod the compound tinc- 

 ture. The powder it unquestionably the most efficacu 



