in botany, a genus of the monogyne order, belonging to the pentandria clas of plants. There are two species. One of them, long remarkable for its bark, so much used in medicine under various names, is a native of some provinces of Peru in South America; the other, whose bark is but lately discovered to have the same medical virtues, is a native of Jamaica. The first was thought for a long time to grow only in the province of Quito, on some hills near the city of Loxa; but it has since been found in other parts of that empire. It is a tree that seldom exceeds 18 feet in height, and is of a proportionable thickness. It grows in forests spontaneously among other trees; and is propagated by seeds which fall to the ground of themselves. Of the other species we have an account in the Phil. Transf. vol. 67, under plate lxiii., the name of Cinchona Jamaicensis. It grows on stony fig. 10. lands near the sea-shore on the north side of the island of Jamaica, and seldom exceeds 20 feet in height. The trunk is not thick in proportion, but hard, tough, and of a yellowish white colour on the inside. The branches and leaves are opposite; the leaves are of a rusty green, and the young buds of a bluish-green hue. It blossoms in November, and continues in flower till February, having on the same tree flowers and ripe pods. The flowers are of a darkish-yellow colour, and the pods black: when ripe they split in two, and are, with their flat brown seeds, in every respect similar to those of the first species, termed cinchona officinalis.

The bark of the cinchona officinalis hath now the highest reputation in the materia medica, and is justly looked upon as an almost universal medicine. It did not, however, acquire this great reputation all at once; nor, in all probability, when first discovered, did the cinchona merit those praises to which it is now so justly intitled. The reason of this is, that within these two centuries, as is observed by Dr Percival, the diseases of the European countries have assumed a new face. Formerly they were mostly of the inflammatory kind; and accordingly we find Dr Sydenham, a most experienced physician, treating almost all diseases in the manner proper for inflammatory ones. In these the Peruvian bark is pernicious. Its general characters are that of an astringent and corroborant; and these qualities necessarily augment inflammatory disorders. Now, to whatever cause it may be owing, diseases seem to arise mostly from a debility of the system, and hence the great efficacy of the bark in our times. At first it was only celebrated as a remedy for intermittent fevers; a long time after, it was discovered to be an antiseptic, to be efficacious in gangrenes, and mortifications, the scurvy, and all diseases in which there is a tendency to putrefaction. In the small-pox it is likewise of excellent use, where nature requires to be assisted in the expulsion of the variolous matter. The famous and bloody matter in the variolous pustules also soon changes its appearance on the use of the bark; which needs only to be withheld if it is found to increase the difficulty of breathing. For the same reason it is exceedingly efficacious in foul old ulcers, very frequently correcting the fancies of them, and changing it into laudable pus. In nervous and putrid fevers, in inflammatory affections also, particularly in ophthalmies of this kind, it has been found to be a remedy of great efficacy. The retrocession of the morbid matter in the measles is said to be powerfully prevented by the use of the bark; but where the lungs are affected, as they frequently are in this disease, the use of it is certainly to be avoided. Dr Percival informs us, that he had a patient who was feized with an intermittent while labouring under a severe gonorrhea. The bark was given him in large quantities; and so far was it from lessening the discharge, that it evidently increased it, and lessened its violence. The late Dr Whytt informs us, that, in 16 days, he swallowed near four ounces of the bark in substance, while labouring under a catarrhous cough, without feeling any bad effects from its astringent quality. In a tertian, attended with a violent cough and spitting, he prescribed the bark in the usual quantity, without its hurting the breast in the smallest degree. And he had repeated experience of its virtues in curing a hoarseness after the measles, when unattended with a fever and difficult respiration. In the hooping cough also, when given early, he found it one of the best remedies; but here we must remark, that in some cases of the hooping cough where we have seen the bark administered, the disease was manifestly increased by it. Perhaps in these the medicine had been too long delayed. The bark has been successfully administered, in the quantity of a drachm every three hours, to a woman two days after her delivery, without lessening the lochia; and it has been frequently given to others during their catamenia, without the least interruption of them. These and other facts are brought by Dr Percival, to prove that the prejudices against the use of the bark, which commonly take their rise from its known astringent quality, are altogether groundless.

As to the chemical analysis of this valuable medicine, the above mentioned author hath taken a great deal of pains to elucidate it. Other chemists had discovered that this, as well as many other vegetable substances, contains a mucilaginous and resinous part; that the former is more soluble in water, and the latter in spirit of wine, &c. Dr Lewis particularly affirms, that the astringency of the Peruvian bark "refuses wholly in its resin, which does not appear to be in any degree soluble in watery liquors." Also, that in making decoctions of the bark, the resin melts out in the first boilings; and that the subsequent ones are transparent and bitter, without the least degree of turbidness or astringency. Both these assertions, however, Dr Percival hath shown to be mistakes. He digested a drachm of powdered bark 48 hours in two ounces of rectified spirit of wine. The clear tincture was then poured off, and fresh spirit, in the same quantity as before, added to the residuum. The digestion was repeated five times, until the menstruum acquired neither taste nor colour from the bark. The powder was then carefully dried and macerated without heat, in two several portions of spring-water, and communicated to each of them the property of striking a purple colour with green vitriol. Both the watery infusions were insipid; from whence Dr Percival concludes, that rectified spirit of wine extracts all the bitternes, but not all the astringency of the bark. To try the power of aqueous menstrua, he infused half an ounce of powdered bark in six ounces of cold spring-water for 48 hours, and boiled another half ounce for about 40 minutes in nine ounces of water. The cold infusion seemed to be at least as strong as the decoction; and a considerable quantity of the resin appeared to have dissolved in the cold water; for when boiled for some minutes over a quick fire, it grew turbid, and deposited a resinous precipitate. He now determined to try whether it was possible to exhaust the bark of Cinchona, its resin by this treatment. Half an ounce of powdered bark was macerated for three days, in six ounces of water. The menstruum was then decanted off, and fresh water added in the same quantity as before. The effusion was repeated at equal intervals 30 times, till the water was insipid, colourless, and unalterable by the addition of green vitriol. The residuum also, when chewed in the mouth, had no sensible bitternes or astringency. Two drachms of this residuum, carefully dried by a very gentle heat, were infused in an ounce of rectified spirit of wine: in two days a tincture, of an orange colour and bitter taste was produced. This experiment was repeated with boiling water; the bark was not exhausted till after the 25th coction; and after all, gave a stronger tincture to spirit of wine than in the former case. These experiments shew how extremely difficult it is to exhaust the bark of its virtues; neither is this only in appearance, but in reality; for the same author informs us, that a quantity of bark, reduced by infusion and decoction to an insipid powder, was given in the dose of two drachms, to a person labouring under a quotidian ague, an hour or two before the coming on of the fit; by which means the disease was changed into a tertian, and at last entirely removed. In short, Dr Percival hath clearly shown, that by one menstruum it is impossible to exhaust Peruvian bark entirely of its virtue; but in order to determine with as much accuracy as possible the relation which different menstrua bear to it, he digested a drachm of the bark in three ounces of several different liquors. After seven days infusion, the clear part of each menstruum was carefully poured off, and the residuum evaporated to dryness. The weight lost by the bark in this experiment was thought to indicate the solvent power of each particular menstruum. The drachm infused in rectified spirit of wine, lost six grains; in French brandy, eight grains and a quarter; in Rhenish wine, nine grains; in water, eight grains; and in water and vinegar, the same quantity.

The doctor also tried a great number of other experiments with regard to the astringency and antiseptic qualities of the bark; from whence he concludes, that its astringency is much less than has been commonly imagined; and that in certain cases, particularly in bilious disorders, the addition of acids to the bark is necessary. Columbo-root he also thinks would be an useful addition in these decoctions. From his experiments it would seem that a cold infusion of the bark is its best preparation; but as that is very agreeable to the taste, the addition of orange-peel and extract of liquorice will be found very convenient; for these are found to cover the ill taste of this drug more effectually than any other.

The virtues of Peruvian bark were discovered by the Indians about the year 1500. A lake near a town in Peru was surrounded by these trees; which were torn up by an earthquake, and falling into the adjacent water, they rendered it bitter. An Indian, urged by his thirst during a fever, under which he laboured, drank of this water, because no other could be had; however, observing that he soon recovered, he related the case, and others were also cured. On this enquiry was made, and to the trees it was found that the water owed its virtue; then it was soon discovered that the bark alone possessed the medicinal quality. In 1649, a Spanish soldier was quartered in an Indian's house, and being seized with an ague, his landlord, moved with compassion, told him of a cure, and with the same he cured his companions. At length the vice-queen, wife of the count de Cinchon, then vice-roy of Peru, was seized with an intermittent fever, this soldier cured her also; hence the name cinchona and comitiflora. After this, father de Lugo brought a parcel of it to Rome, and from him it also received the name of cert. card. de Lugo. From Rome it was spread into France and England, and at length became general.

This bark is brought in pieces of different sizes, some rolled up in thick quills, and others flat; the outside is brownish, and generally hath a whitish moss spread on it; the inside is of a yellowish, reddish, or rusty iron colour. The best sort is bitter, resinous, breaks close and smooth, is friable betwixt the teeth, pulverizes easily, when powdered is of a cinnamon colour, but rather paler; and, according to the opinion of some, as the surest test of its goodness, it hath a nutty kind of smell, and at the same time so much of the aromatic, as not to be disagreeable. The inferior kinds, when broken, appear woody, and in chewing separate into fibres. That which is called female bark, is redder in the inside; it is also thicker; and on the outside more white and smooth; is weaker to the smell and taste than the above; and, in medical virtue, greatly inferior.—The bark of the cinchona Jamaicensis is found to yield its virtues much better to watery menstrua than the officinalis; and, as far as has yet been tried, seems not inferior in efficacy.