Cinchona, otherwise called Peruvian or Jesuits' Bark. According to some, the Peruvians learned the use of this bark by observing certain animals affected with intermittents instinctively led to it; whilst others say, that a Peruvian having an ague, was cured by happening to drink of a pool which, from some trees having fallen into Cinchona, it, tasted of cinchona; and its use in gangrene is said to have originated from its curing one in an aguish patient. About the year 1640, the lady of the Spanish viceroy, the Countess del Cinchon, was cured by the bark, which has therefore been called Cortex or Pulvis Compositus Cinchona, Cinchonina or Chinchina, Kinakina or Rinkina, Quinquina or Quinquina; and from the interest which the Cardinal de Lugo and the Jesuit fathers took in its distribution, it has been called Cortex or Pulvis Cardinalis de Lugo, Jesuiticus, and Patrum.

On its first introduction into Europe it was reprobated by many eminent physicians, and at different periods long afterwards, it was considered as a dangerous remedy; but its character, in process of time, became universally established. For a number of years the bark, which was rolled up in short thick quills, with a rough coat, and a bright cinnamon colour in the inside, which broke brittle, and had an aromatic flavour, a bitterish astringent taste, with a degree of aromatic warmth, was esteemed the best; though some considered the large pieces as of equal quality. In the year 1779, the Hussar frigate took a Spanish ship, loaded principally with Peruvian bark, which was much larger, thicker, and of a deeper reddish colour, than that in common use. Soon after it was brought to London, it was tried in St Bartholomew's hospital, and in other hospitals about town, and was said to be more efficacious than the quill bark. This put practitioners upon examining into the history of the bark, making experiments with it, and instituting comparative trials of its effects with those of the bark in common use on patients labouring under intermittent complaints. In July 1782, Dr William Saunders published an account of this red bark, in which he says that the small quill bark used in England is either the bark of the young trees, or of the twigs or branches of the old ones, and that the large bark, called the red bark from the deep colour, is the bark of the trunk of the old trees; and he mentions a Mr Arnot, who had himself gathered the bark from the trees in Peru, and M. Condamine, who gives an account of the tree in the Memoirs of the Academy of Sciences at Paris for the year 1738; both of whom say, that, taking the bark from an old tree effectually kills it; but that most of the young trees which are barked recover, and continue healthy; and that, for these reasons, the Spaniards now bark the younger trees for foreign markets, though they still imported into Spain some of the bark of the old trees, which they esteemed as much more efficacious than that which was obtained from the young. From these accounts Dr Saunders concludes, that the large red bark brought to London in the year 1779 was of the same kind as that used by Sydenham and Morton; as it answers to the description of the bark used in their time, which is given by Dale and other writers on the materia medica, who were their contemporaries. Dr Saunders says, that it is not only stronger and more resinous, but likewise more efficacious and certain in its effect, than the common bark, and that it had cured many agues after the other had failed.

A species of cinchona has also been discovered in the West India islands, particularly in Jamaica. It is accurately described by Dr Wright, under the title of Cinchona Jamaicensis, in a paper published in the Philosophical Transactions. In Jamaica it is called the sea-side beech, and grows from twenty to forty feet in height. The white, furrowed, thick outer bark is not used; but the dark brown inner bark has the common flavour, with a mixed kind of a taste, at first of horse-radish and ginger, but becoming at last bitter and astringent. It seems to give out more extractive matter than the cinchona officinalis. Some of it was imported from St Lucie in consequence of its having been used with advantage in the army and navy during war; and it has been treated of at considerable length by Dr Kentish, under the title of St Lucia Bark. The fresh bark is found to be considerably emetic and cathartic, which properties it is said to lose on drying.

The pale and the red are chiefly used in Britain. The pale is brought to us in pieces of different sizes, either flat or quilled, and the powder is of rather a lighter colour than that of cinnamon. The red is generally in much larger, thicker, flattish pieces, but sometimes also in the form of quills, and its powder is reddish, like that of Armenian bole. As already observed, it is much more resinous, and possesses the sensible qualities of the cinchona in a much higher degree, than the other kinds; and the more nearly these kinds resemble the red bark, the better they are now considered. The red bark is heavy, firm, sound, dry, and friable between the teeth; it does not separate into fibres, and breaks, not shivery, but short, close, and smooth. It has three layers; the outer is thin, rugged, of a reddish-brown colour, but frequently covered with mossy matter; the middle is thicker, more compact, darker-coloured, very resinous, brittle, and yields readily to the pestle; the inmost is more woody, fibrous, and of a brighter red.

Practitioners have differed much with regard to the mode of operation of the Peruvian bark. Some have ascribed its virtues entirely to a stimulant power. But while the strongest and most permanent stimuli have by no means the same effect with bark in the cure of diseases, the bark itself shows hardly any stimulant power, either from its action on the stomach, or on other sensible parts to which it is applied. From its action on dead animal fibres, there can be no doubt of its being a powerful astringent; and from its good effects in certain cases of disease, there is reason to presume that it is a still more powerful tonic. To this tonic power some think that its action as an antiseptic is to be entirely attributed; but that, independently of this, it has a very powerful effect in resisting the septic process to which animal substances are naturally subjected, appears beyond all dispute, from its effects in resisting putrefaction, not only in dead animal solids, but even in animal fluids when entirely detached from the living body.

But although it be admitted that the Peruvian bark acts powerfully as an astringent, as a tonic, and as an antiseptic, yet these principles will by no means explain all the effects derived from it in the cure of diseases. Accordingly, from no artificial combination in which these powers are combined, or in which they exist even in a high degree, can the good consequences resulting from Peruvian bark be obtained. Many practitioners, therefore, are disposed to view it as a specific. If by a specific, however, we mean an infallible remedy, it cannot indeed be considered as entitled to that appellation; yet in as far as it is a very powerful remedy, of the operation of which no satisfactory explanation has yet been given, it may with great propriety be denominated a specific. But whatever its mode of operation may be, there can be no doubt that it is daily employed with success in a great variety of diseases. The remedial value of quinine, particularly in the form of a sulphate, is known to every one, and will be fully explained in the proper place.

This bark was first introduced for the cure of intermittent fevers; and in these, when properly exhibited, it rarely fails of success. Practitioners, however, have differed with regard to the best mode of exhibition; some prefer giving it just before the fit, some during the fit, others immediately after it. Some, again, order it in the quantity of an ounce between the fits, the dose being the more frequent and larger according to the frequency of the fits; and this mode of exhibition, although it may perhaps sometimes lead to the employment of more bark than is necessary, is considered as upon the whole preferable, from being best suited to most stomachs. The requisite quantity is Cinnamon, very different in different cases; and in many vernal intermittents it seems even hardly necessary.