Jalap

JALAP, a cathartic drug consisting of the tuberous roots of Ipomaea purga, a convolvulaceous plant growing on the eastern declivities of the Mexican Andes at an elevation of 5,000ft. to 8,000ft. above the level of the sea. The jalap plant has slender herbaceous twining stems, with alternately placed heart-shaped pointed leaves and salver-shaped deep purplish-pink flowers. The underground stems are slender and creeping; their vertical roots enlarge and form turnip-shaped tubers. The roots are dug up in Mexico throughout the year, and are suspended to dry in a net over the hearth of the Indians' huts, and hence acquire a smoky odour. The large tubers are often gashed to cause them to dry more quickly. In their form they vary from spindle-shaped to ovoid or globular, and in size from a pigeon's egg to a man's fist. Externally they are brown and marked with small transverse paler scars, and internally they present a dirty white resinous or starchy fracture. The ordinary drug is distinguished in commerce as Vera Cruz jalap, from the name of the port whence it is shipped.

Jalap has been cultivated for

many years in India, chiefly at Ootacamund, and grows there as easily as a yam, often producing clusters of tubers weighing over 9 lb. ; but these, as they differ in appearance from the commercial article, have not as yet obtained a place in the English market. They are found, however, to be rich in resin, containing 18%. In Jamaica also the plant has been grown, at first amongst the cinchona trees, but more recently in new ground, as it was found to exhaust the soil.

Besides Mexican or Vera Cruz jalap, a drug called Tampico jalap has been imported for some years in considerable quantity. It has a much more shrivelled appearance and paler colour than ordinary jalap, and lacks the small transverse scars present in the true drug. This kind of jalap, the Purga de Sierra Gorda of the Mexicans, was traced by Hanbury to Ipomaea simulans. It grows in Mexico along the mountain range of the Sierra Gorda in the neighbourhood of San Luis de la Paz, from which district it is carried down to Tampico, whence it is exported. A third

variety of jalap known as woody jalap, male jalap or Orizaba root, or by the Mexicans as Purgo macho, is derived from Ipomaea orizabensis, a plant of Orizaba. The root occurs in fibrous pieces, which are usually rectangular blocks of irregular shape, tin. or more in diameter, and are evidently portions of a large root. It is only occasionally met with in commerce.

The dose of jalap is from five to 20 grains, the British Phar macopeia directing that it must contain from 9 to 11% of the resin, which is given in doses of two to five grains. One prepara tion of this drug is in common use, the Pulvis jalapae composites, which consists of 5 parts of jalap, 9 of cream of tartar and 1 of ginger. The dose is from 20 grains to a dram. It is best given in the maximum dose which causes the minimum of irritation.

The chief constituents of jalap resin are two glucosides convolvulin and jalapin—sugar, starch and gum. Convolvulin constitutes nearly 20% of the resin. It is insoluble in ether, and is more active than jalapin. It is not used separately in medicine. Jalapin is present in about the same proportions. It dissolves readily in ether, and has a soft resinous consistence. It may be given in half-grain doses. It is the active principle of the allied drug scammony. According to Mayer, the formula of convolvulin is and that of jalapin Jalap is a typical hydragogue purgative, causing the excretion of more fluid than scammony, but producing less stimulation of the muscular wall of the bowel. For both reasons it is preferable to scammony. It is a powerful cholagogue, an action possessed by few hydragogue purgatives. The drug is largely employed in dropsy from any cause, being especially useful when the liver shares in the general venous congestion. It is not much used in ordinary constipation.