JALAP. In Mexico, from 4000 to 6000 feet above the sea level, grows the plant which yields true jalap, and which has been called by botanists Convolvulus purga, and Ipomoea purga, the latter name being adopted by De Candolle. It has since, however, been placed in the genus Exogonium. The true jalap (Exogonium purga) has a tuberous, perennial root, a smooth, twining, annual stem, a salver-shaped corolla, with long cylindrical tube, a calyx of five small, unequal sepals, and herbaceous stems. Its leaves resemble the ivy, and its beautiful red flowers open only at night. The dried tubers of this plant supply the drug jalap, so named from Jalapa, a town in Mexico, where it abounds, and which is the only market for the tubers. These, as found in commerce, rarely exceed 1 lb. in weight; they are oval in form, and covered with a dark skin or cuticle. Internally they are yellowish gray, with deep brown concentric circles, and are hard and difficult to powder. Inferior sorts are more irregular in form, and are called spurious jalap, or, from their shape, cocked-hat jalap. Some roots are much worm-eaten, and are so called; but, as the insects do not touch the resinous portions, such roots are available for extracts.
Four kinds of jalap are known in English commerce, two genuine and two spurious,—first, dark, heavy, resinous tubers; secondly, lighter coloured and less resinous; thirdly, white or false jalap, pieces of which are occasionally mixed with the true; and, fourthly, jalap-stalk or woody jalap, the slices of which are more fibrous and woody than the genuine. There are about 200,000 lbs. of the pure jalap annually exported from Vera Cruz on the Gulf of Mexico, the seaport of Jalapa.
The resinous portion, jalapine, is the active ingredient of jalap. It is obtained by mixing the alcoholic tincture of jalap (prepared by percolation or digestion) with water. The precipitated resin is to be washed in warm water, and then mixed with alcohol. By evaporation the tincture yields the resin, which, according to Mayer, who names it rhodeoretine, consists of C. 72, H. 60, O. 27. It is insoluble in ether, and is convertible by the action of alkalies into rhodeoretic acid, which is soluble in water. The powdered root of jalap, as well as the resin, is a local irritant: in the human subject jalap acts as a powerful and drastic purgative, 3 or 4 grains of the resin sufficing for the purpose. Jalap is tolerably certain in operation, and does not disorder the system so much as some other purgatives, the effect being principally confined to the alimentary canal. It is used as a vermifuge; also in cerebral affections, dropsies, and some other diseases. The dose of jalap, in powder, is, for an adult, from 10 to 30 grains; for young children, from 2 to 5 grains. Jalap is sometimes exhibited in gingerbread; such are the purgative cakes, and the biscuits purgatifs of England and France. (C. T.)
JALAPA or XALAPA, a town of Mexico, capital of a cognominal department, in the state of Vera Cruz. It is situate on a small plain at the foot of a range of hills 55 miles N.W. of the town of Vera Cruz, and about 4500 feet above the sea level. On account of its exhilarating climate it is a favourite resort of the inhabitants of Vera Cruz when the romito prieto is prevalent there. The only building of importance is an old church, which is believed by the people to have been founded by Cortes. Cotton is manufactured, but its trade has greatly diminished. In the neighbourhood grows the creeping-plant, Exogonium purga, or, as it is called from this town, Jalap. The population of the department is estimated at 45,000, and of the town, at 16,000 persons.