History:  It is only within comparatively recent years that any certainty has existed in relation to the plant from which jalap root is obtained. It was first spoken of in 1609, as Bryonia mechoacana nigricans, then it was regarded by Ray as Convolvulus Americanus jalapium dictus, after which Tournefort, being deceived by persons who asserted that they had seen the plant growing, referred it to a species of Mirabilis. Balfour placed it as the Exogonium purga, and Linnaeus named it Convolvulus jalapa, and thus much difference of opinion existed until, in 1827, when Dr. J. R. Coxe, of Philadelphia, succeeded in obtaining perfect flowers from roots of the true plant furnished to him from their native soils, and thus first made its true character known to the scientific world.

The name of Ipomoea purga was bestowed upon the plant by Wenderoth and Hayne, but as the authorities of this country have, undoubtedly, the first claim, it may be viewed as fixed that I. jalapa, the name originally given to it by Nuttall, is the official plant.

The jalap plant is found in a deep, rich, vegetable soil, at an elevation of nearly 6000 feet above the level of the sea, growing in Mexico, near Chicanquiaco and Xalapa, from which last named place it is usually exported, and from which it has also obtained its name. It is generally imported in bags, containing 100 or 200 pounds. The root is the official part, and is gathered in all seasons, but principally in March and April, when the young shoots are appearing. The plant may be cultivated in the southern parts of the United States.

In 1866, Dr. D. Hanbury planted a root or tuber of Jalap in a garden, near London, and obtained promising results. It is now successfully grown in Jamaica and in India, especially in the Nilgherry hills of that country.

According to Warden (1887), the jalap tubers of India are not of first quality. Jalap is a very variable drug, much of it being of an inferior quality. The best kind is that known as the Vera Cruz variety. Several related, and often inferior drugs, e. g., Tampico jalap, have appeared on the market.

When fresh, the root is black externally, white and milky within, and varies in size according to its age, from that of a walnut to that of a moderate-sized turnip. It is dried in net bags over the fire, sometimes whole, and sometimes in sections. It is often preyed upon by insects which, however, leave its active part untouched, rendering it consequently more energetic. Jalap thus preyed upon is used for procuring the resin, but should not be given internally, except in much smaller doses than for the ordinary root.

Jalap is rather difficult to polvorize, but if triturated with cream of tartar, sugar of milk, or other hard salt, the process of polvorization is facilitated, and the powder rendered much finer. When in powder, the color is a pale grayish-brown, and when in contact with the mucus membrane of the air-tube, causes coughing and sternutation, with an increased discharge of saliva. Its solvents are water, alcohol, or spirits. Water takes up a small portion of its cathartic principle, but considerable of an amylaceous and mucilaginous extractive matter. Alcohol dissolves the resin, on which its cathartic virtues depend. Ether only partially dissolves it. Diluted alcohol completely extracts its active properties.

When applied to a wound, it is said to induce purgation. Notwithstanding its activity, it is a safe and convenient purgative, much in use among the profession, and is useful in all cases where it is desirable to produce an energetic influence on the bowels, or to obtain large evacuations.

If intestinal inflammations are present it should not be used.

United with the bitartrate of potassium, its hydragogue properties are much increased, and thus it proves beneficial in dropsies, as well as in some forms of scrofula. Jalap, however, is suitable for excitable, active conditions, and may be used where a cooling effect is desired, as when it is necessary to evacuate the bowels in febrile disorders.

Inflammatory conditions of the biliary apparatus are exceptions to the rule that it should not be used in gastro-intestinal inflammations. When the rectum is impacted with a hard, fecal mass, the expulsion of the latter is facilitated by the purgative action of jalap, which greatly augments the intestinal secretions; all cases of constipation, due to dryness of the mucus membranes, through inactivity of the intestinal glands, are relieved by jalap. The dose for this latter purpose may be 5 grains in the morning, repeated for several days. When a stimulating laxative can not be used because of hemorrhoids, jalap may be employed, and it is likewise efficient as a derivative in cerebral disorders.

It is stated that the aqueous extract of jalap, the root having been previously exhausted of its resin by alcohol, will exert no cathartic influence, but will operate as a powerful diuretic, but I have not been able to procure this effect, though having made a trial in several cases (King). Three grains of jalap, taken an hour before each meal, act as a slight nauseant, destroying a desire for food among persons who are apt to eat too freely. If jalap is digested in ether, its nauseous taste and smell will be wholly removed without lessening its cathartic power. A biscuit is sometimes made for those to whom it is extremely nauseous and disagreeable; 5 drachms of jalap, 30 of sugar, and 4 ounces of flour, are made into 15 biscuits after the usual mode; 1 biscuit is a dose. The tendency of jalap to gripe and nauseate, may be obviated by adding to the dose 1 or 2 grains of camphor, or 3 grains of cloves. The dose of powdered jalap is from 10 to 30 grains (the aqueous extract ought not to be used, except as a diuretic)of the tincture, from 1 to 4 fluid drachms; the resin, or alcoholic extract, is given in from 2 to 8-grain doses, being usually rubbed up with sugar, or in emulsion, for the purpose of lessening its disposition to produce painful irritation of the intestinal mucus membrane.

As a hydragogue, 2 drachms of the bitartrate of potassium are added to 10 or 30 grains of polvorize jalap. Convolvulin (rhodeoretin) purges violently in 3 or 4-grain doses, and appears to be the active principle of jalap. Specific jalap, 10 to 20 drops every 4 hours for its specific uses. Though not an anthelmintic, jalap is often given to hasten the expulsion of worm, after agents have been given for their stupefaction or destruction.

The active principles of this plant are unknown. It possesses mild cathartic properties, acting gently in doses of from 40 to 60 grains of the powdered root. The infusion taken in wineglassful doses every hour, has been effective in dropsy, strangury, and calculous affections. It seems also to exert an influence over the lungs, liver, and kidneys, without excessive diuresis or catharsis. The saturated tincture is more energetic than the powdered root, decoccion, or extract. It is asserted that the Indians can handle rattlesnakes with impunity after wetting their hands with the milky juice of this root.