in botany, a genus of the pentandria monogynia clasps. The corolla is bell-shaped; and the capsule is below the flower, and opens at the base. There is but one species, viz. the officinalis, a native of Peru. The Peruvian bark, which is the bark of this tree, is brought to us in pieces of different sizes, sometimes rolled up into short thick quills, and sometimes flat: the outside is brownish, and generally covered in part with a whitish mould; the inside is of a yellowish, reddish, or rusty iron colour. It has a lightly aromatic smell, somewhat musty, yet not disagreeable; a bitterish, astringent taste, which dwells long upon the tongue, accompanied with a degree of aromatic warmth. The small, thin, flat pieces are by some accounted the best; by others, the quill sort, with the rougher coat, especially if of a bright cinnamon colour on the inside; though the large flat pieces, whether rough or smooth, of a lighter or darker colour, are often of equal goodness. The best bark is that which is strongest in smell and taste: this likewise proves friable betwixt the teeth, and does not separate into fibres; it breaks, not shivery, but close and smooth.

The virtues of this bark, as a febrifuge, were discovered by the Indians about the year 1500: Europe did not become acquainted with it till 1649: nor was it received into general practice till several years after this; some ill consequences ensuing from its imprudent use, having brought it for a time into disrepute. At present, it is looked upon as the most effectual remedy in intermittent fevers of almost every kind, and safe in all ages and constitutions; provided it be judiciously and seasonably administered, and due regard be had to the circumstances of the disease. The modern practice, previous to the use of this medicine, usually gives an emetic at the beginning of a paroxysm: in some cases a cathartic, and in plethoric habits vexation, are premised: these render the bark not only more safe, but likewise more certain and speedy in its operation: where these evacuations are neglected, or not sufficiently plentiful, the disease, if of long standing, standing, scarce yields to the cortex; or if it appears at length subdued, yet the patient does not recover his strength, and soon suffers a relapse. The use of the bark is begun at the end of a paroxysm, and repeated, in the quantity of half a dram (more or less, according to the circumstances of the patient) every third or fourth hour during the intermission: where the fever is of the bilious kind, and accompanied with great heat, a little nitre is joined: in all cases, moderate exercise generally promotes its effect. At first, it usually looftens the belly, and sometimes operates as if a cathartic had been taken; and by this means supplies the omission of evacuations before its exhibition: if the purging continues, the medicine does not answer the purposes intended by it: in such case, a little opium is added, which effectually suppresses the flux: if after this the patient continues too coltive, recourse is had to glysters. The looseness, however, ought not to be stopt too soon: on the contrary, where the bark does not itself produce this effect, it is necessary, as Dr Mead informs us, to join to it a little rhubarb, so as to occasion for a time two stools a day; by this means the disease is more effectually cured, and left subject to be followed by a dropfy, or ill habit of body: after a dram or two of rhubarb have been taken, it is to be discontinued, and the bark exhibited by itself. After the fever has been removed, the medicine is continued for some time longer, to prevent a relapse; and evacuations, unless absolutely necessary, abstained from. The disease is nevertheless seldom completely cured before some very considerable evacuation, either by stool, urine, or perspiration, ensues: if this does not succeed spontaneously, cathartics, diuretics, or diaphoretics, are given in conjunction with the bark; otherwise the patient continues weak, and without appetite, till either the disease returns, or changes into one of a different kind.

In symptomatic agues, hectic and purulent fevers, cacochymic habits, and where the hypochondres are swelled and distended, this medicine is improper, and for the most part prejudicial. Its manifest affrigrency forbids its use in obstructions of the abdominal viscera, or suppression of any critical evacuation; until the obstruction is first removed, or the evacuation had its due course.

In acute, inflammatory, or malignant fevers, the bark does not seem to have any good effect. Nevertheless, in the decline of long nervous fevers, or after a remission, when from bad habit, old age, fatigue, or the like, the patient is extremely weak, and the pulse low, the cortex proves a medicine of excellent service; provided that there is no extravasation, that the vessels remain entire, and pus is not already formed.

Peruvian bark has likewise been found eminently serviceable in gangrenes and mortifications, proceeding either from an internal or external cause. In all the cases of this kind, where it proved successful, it occasioned a kind suppuration, which degenerated when the use of the medicine was discontinued, and again turned kindly upon resuming it. Some have been hence induced to try the cortex in various cases, where either the pustules did not rightly suppurate, or petechiae shewed a disposition to a gangrene; and here likewise it answered expectation: the empty vesicles filled with matter, watery fancies changed into thick white pus, the petechiae became gradually of a pale colour, and at length disappeared, and the pox began to turn sooner than was expected.

The bark has been applied likewise, and not without success, to the cure of periodic head-aches, hysterics and hypochondriac fits, and other disorders, which have regular intermissions. By its affrigrency and aromatic quality, it strengthens the whole nervous system, and proves useful in weakness of the stomach, and sundry chronic disorders, proceeding from too great laxity of the fibres. In obstinate uterine fluxes, and old gleets, bark joined with chalybeates has notable effects.

The virtues of Peruvian bark reside chiefly in a resinous substance, and hence are extracted in perfection by rectified spirit. By strong cotion in water, the resin is melted out, and mingled with the water; which whilst hot appears transparent, but in cooling grows turbid, and deposits great part of the resin to the bottom. Water elevates in distillation the aromatic part of the bark; pure spirit brings over nothing. Hence an aqueous extract proves not only less in quantity, but likewise inferior in quality to one made with rectified spirit. Proof-spirit extracts the virtues of this drug in tolerable perfection, in the cold; heat enables it to take up more than it can retain when cold. Spirit of sal ammoniac, prepared with fixed alkaline salts, gains very little from the cortex, either with or without heat; the spirit prepared with quicklime, and the dulcified spirit, in a few hours become strongly impregnated with its smell and taste.

The official preparations of bark are an extract resin, spirituous tincture, tincture in volatile spirit, and compound tincture. It is an ingredient also in the stomachic tincture.

The substances usually joined with bark in prescription seem calculated either to promote its efficacy, or merely for reducing it into the intended form; without much regard to its agreeableness, and the convenience of taking it: this is nevertheless a point of great consequence, as its taste, and the quantity which is necessary, make the patient too frequently loath it, before enough has been taken to produce the desired effect. If designed to be given in the solid form of a bolus, electuary, &c., it should be made up, not, as is customary, with syrups, but with mucilages: with the former, it sticks about the mouth and fauces, whence its taste remains for a considerable time; with the latter, it passes freely, scarce leaving any taste in the mouth. Aromatics do not prevent the taste of the bark from discovering itself; extract of liquorice very effectually conceals it. The extract of logwood also, joined to that of bark, and a proper quantity of mucilage, form a very elegant and agreeable composition.