(From contra and yerva, a herb, Spanish). A herb good against poisons. Drakena, Cyperus, longus odorus Peruanus, dorstenia, bezoardi-ca radix. Counter poison. It is the dorstenia con-trayerva Lin. Sp. Pi. 176.

The contrayerva was first brought into Europe about the year 1581 by sir Francis Drake, whence its name Drakena. It is the root of a small plant found in Peru, and other parts of the Spanish West Indies. There are two kinds; the one placenta ovali, the other angulari et undulata. The sort generally brought to us is about an inch or two long, half an inch thick, full of knots, surrounded on all sides with numerous long tough fibres, most of which are loaded with scaly knobs, of a reddish brown colour on the outside, and pale within.

The tuberous parts of these roots are the strongest, and should be chosen for use. They have an agreeable aromatic smell; a rough, bitter, penetrating taste; and, when chewed, they give out a sweetish kind of acrimony.

It is diaphoretic and antiseptic; formerly used in low nervous fevers, and those of the malignant kind; though taken freely it does not produce much heat. It is, however, now seldom used; though, with the Peruvian bark in decoction, we have sometimes employed it in ulcerated sore throats as a gargle.

Dr. Cullen observes, that this and serpentaria are powerful stimulants, and both have been employed in fevers in which debility prevailed. However, he thinks, wine may always supercede the stimulant powers of these medicines; and that debility is better remedied by the tonic and antiseptic powers of cold and Peruvian bark, than by any stimulants.

By the assistance of heat, both spirit and water extract all its virtues, but they carry little or nothing in distillation; extracts made by inspissating the decoction retain all the virtues of the root.

The London college forms the compound powder of contrayerva, by combining five ounces of contrayerva in powder, with a pound and a half of the compound powder of crabs' claws.

This powder was formerly made up in balls, and called lapis contrayervae; employed in the decline of ardent fevers, and through the whole course of low and nervous ones. The radix serpentariae Virginiensis in all cases may be substituted for the contrayerva. See Lewis's Materia Medica; Neumann's Chem. Works: Raii Hist. and Cullen's Mat. Med.

Contrayerva nova, or Mexican contrayerva. It was introduced into Europe after the former, and is brought from Guiana, as well as from Mexico. The root is longish, about two fingers thick, externally rough, and of a brownish colour, internally white, with a pith in the middle, of a sweetish aromatic taste, and but little inferior to the contrayerva introduced before it. This is the root of the psoralea pentaphylla Lin. Sp. Pi. 1076.

Contrayerva alba. Contrayerva Germano'-rum. See Asclepias.

Contrayerva Virginiana. See Serpentaria Virginiana.