Peruvian Bark, or Jesuits' Bark, a well-known medicine obtained from the Cinchona, a native of South America and the West Indies. Of this valuable tree, botanists have discovered ten species ; but the following only deserve particular notice, viz.

1. The officinalis, or Peruvian Bark-tree, which was introduced into Europe by the Jesnits.—It is of eminent use in fevers, especially in intermittents, which it seldom fails to remove, provided it be properly administered. The doses vary according to the age of the patient, the violence of the disorder, and other circumstances ; but, in vernal agues, this drug is often unnecessarily swallowed.

Peruvian bark operates differently on various constitutions: sometimes it causes vomiting, in which case it will be advisable to take it in Port-wine, with a view to check nausea or retching. If it induce looseness, such effect may be counteracted by combining the bark with opium; and should it oppress the stomach, this inconvenience may be remedied by the addition of some' aromatic. Beside its use in febrile disorders, bark has frequently been found of service in the confluent small-pox, by promoting the eruption, and suppuration of the pustules, while it tends to abate the violence of the fever. Nor has it been found less useful, both internally and exter-nally, in every scenes of gangrene, if employed in sufficient quantities. Farther,- this drug has often been successfully administered in contagious dysenteries ; in passive hemorrhages, for obviating the disposition to nervous or convulsive diseases; and, when combined with the vitriolic acid, it has been of essential service in the rickets, scrophula, ill-conditioned ulcers, and the first stage of pulmonary consumption: in the last mentioned cases, however, it will be advisable to adopt a milk-diet.— Peruvian bark pays, on importation, a duty of 9 1/2d. per lb.

2. The Caribaea v. Jamaicensis, Caribbean or Jamaica Bark-tree, grows to the height of fifty feet.—The bark obtained from the trunk abounds with fibres, and is more woody than that from the branches and roots: the latter, when dried, breaks more easily, and is pulverized with greater facility than the Peruvian. The Jamaica-bark is produced in the utmost perfection on the north side of that island, where it is highly esteemed, on account of its very agreeable bitter, answering every purpose of that imported from Peru : nor does the former occasion any oppression at the stomach, vomiting, or nausea, but checks such disagreeable sensations in remitting fevers ; and also in other cases where the stomach is disordered.

3. The Trifiora, or Triple-flowered Bark-tree, Is likewise a native of Jamaica, where it grows in the district of Manchineel, to the height of about thirty-five feet. Its bark is considerably thinner, and also more fibrous and red, than cither of the preceding sorts ; and, on being pulverized, assumes a deep cinnamon colour. It possesses a musty, bitter, and astringent taste, and has been given for the cure of fevers, in doses of 20 grains, to adults ; but, as it occasions great nausea and sickness, it is seldom employed.

4. The Floribunda, or St. Lucia Bark-tree, produces a very thin, fibrous rind, which possesses an extremely nauseous bitter taste, and is remarkably astringent. When fresh, it proves a violent emetic; of which property it is not totally divested by age. This drug has cured both intermittent and remitting fevers, that had resisted the Peruvian bark : it is, however, seldom used, excepting in its native island; or in cases where the latter has either failed to afford relief, or cannot be easily procured.

5. The Brachycarpn, which was discovered about sixteen years since by Mr. Lindsay, an eminent surgeon and botanist, then of Westmoreland, in Jamaica. It seldom exceeds eight or ten feet in height; its bark is, externally, smooth and brown ; internally, .it resembles that of Peru in colour, but is more fibrous.—This species is less bitter, and more astringent than the common bark, and has been given by Mr. L. in doses of 25 or 30 grains, with the greatest success, in intermittent, as well as remitting fevers. He has also administered it, with advantage, in the forms of tincture and of decoction, in various cases of dyspepsy or indigestion. If, therefore, a sufficient supply of this drug could be obtained, it might prove an excellent substitute for the Peruvian bark.