6S Medical Botany, 



at the felling of the wood, had distinguished, according to the custom of 

 the countr}', the different kinds of trees by chewing their barks ; and thaty 

 on such occasions, they had taken notice of the considerable bitterness of 

 the Cinchona. The medical practitioners among the missionaries, it is said, 

 tried an infusion of the Cinchona in the tertian ague. This tradition i& 

 thought to be less improbable than that which ascribes the discovery of its 

 medicinal powers to the Indians ; but why we cannot tell, unless it be that 

 the civilised Europeans, and especially the English, are unwilling to admit 

 the sagacity of any people whom they happen to consider in a savage state. 

 Cinchona bark is stripped from the trunk and branches in the dry season j 

 dried in the sun, and sent to Europe in chests, in pieces 5 or 6 in. long, 

 singly or doubly convoluted. There are eight kinds, distinguished in com- 

 merce chiefly by their colours and textures. By analysis, this bark contains 

 a basis of " woody fibre, combined with v/hich are various principles capa- 

 ble of being extracted by different solvents. The taste of all is more or less 

 bitter and astringent. Boiling v/ater extracts all their active principles, 

 affording a solution of a pale brown colour ; this infusion is transparent 

 when hot, but on cooling becomes turbid, and a precipitate is deposited 

 which is soluble in alcohol. The decoction has a very astringent taste, and 

 a deep brown colour. By long boiling, the virtues of the bark are nearly 

 destroyed, owing to the chemical change and precipitation of its active 

 matter. Alcohol, in all its modifications, is a powerful solvent of the active 

 principles of Cinchona, A saturated solution of ammonia is also a solvent 

 of them ; but acetic acid acts less imperfectly than even water." 



" From the experiments of Vauquelin, Fabroni, and others, it appears 

 that the active principles of cinchonas consist chiefly of cinchonian resin, 

 extractive, gluten, a very small portion of volatile oil, and tannin. Vau- 

 quelin has determined the presence of a peculiar acid, to which he gives the 

 name of Mnic acid in some varieties of the bark. The pale bark contains 

 cinchonine, but a very small portion of quinine ; the alkali, again, which 

 predominates in the yellow bark is quinine ; while in the red bark, and 

 some spurious kinds, there is a combination of both, these substances. The 

 presence of cinchonine, as a distinct vegetable principle, was first discovered 

 in Peruvian bark, by Dr. Duncan of Edinburgh. The separation of cin- 

 chonine from the pale bark, and of the quinine from the yellow, is a very 

 simple operation. It consists in digesting the bark, coarsely powdered, in 

 weak sulphuric acid ; and then to repeat this digestion with about half the 

 quantity of liquid, till all the soluble matter is extracted. To this decoc- 

 tion a" small quantity of powdered slacked lime is added, somewhat greater 

 than is necessary to saturate the acid : the precipitate that ensues (a mix- 

 ture of cinchonine and the sulphate of lime) is collected, dried, and boiled 

 a few minutes in alcohol, which takes up the cinchonine, but will not dis- 

 solve the sulphate of lime ; the solution is decanted off ivliile still hot, and 

 fresh portions successively added for the repetition of the same operation, 

 until it ceases to act on the residuum, which is then merely sulphate of 

 lime. Quinine may be obtained from the yellow bark in the same manner 

 that cinchonine is prepared from the pale bark, or by adding an alkali to a 

 solution of the sulphate of quinine. Quinine is not crystallisable like cin- 

 chonine ; but, on the application of heat, it melts into a kind of paste. It 

 has a much more bitter taste than the other, and is very sparingly soluble 

 in water. Pure quinine is very seldom used in medicine ; but the sulphate 

 possesses, in a very eminent degree, the medicinal properties of Peruvian 

 bark, one grain or one grain and a half being equivalent to a drachm of the 

 bark in substance. In Paris it has superseded, in a great measure, the 

 Peruvian bark j and is now extensively used in this country, in all cases 

 where that valuable medicine is indicated, in doses of from 2 to 3 grains. 

 Peruvian bark has been long known as one of the most powerful and valu- 

 able toni£s we possess, and may be administered with great freedom in all 



