Active Ingredients. - Jalap contains about 15 per cent. of a resin upon which its cathartic properties depend; also about 20 per cent. of a watery extractive matter, with starch, sugar, and other substances of minor importance.

The pure resin (that of the true jalap plant) is of a grayish color, acrid, brittle, and opaque. It is soluble in alcohol; slightly soluble in ether; readily so in nitric and acetic acid, and in solutions of potash; but in water and in oil of turpentine it is not soluble. Sulphuric acid turns it crimson.

Jalap also contains a strongly purgative substance called convolvuline (rhodeoretine of the German chemists), colorless, transparent, insoluble in ether, and having for its formula, C31H50O16. It has a slightly acid reaction, and exhibits the chemical characteristics of a glucoside.

Spurious, or fusiform, jalap, the product of the Convolvulus Oriza-bensis, has for its chief ingredient jalapine, already described as the active ingredient of scammony.

Physiological Action. - Jalap is a well-known and valuable cathartic, and one upon which great reliance can be placed. In full doses it produces nausea, vomiting, griping in the alimentary canal, often attended by colic and flatulent rumbling, with copious liquid and sour evacuations from the small intestines, and in less degree from the large ones. The action is not accompanied by any febrile symptoms; it is said, also, that constipation less frequently follows the employment of jalap than of most other purgatives. The watery extract prescribed by the Dublin Pharmacopoeia is said to purge without griping, and therefore to be well adapted for administration to children. Compared with other medicines, the operation of jalap closely resembles that of scammony. It is more drastic than senna, and less irritant to the mucous membrane than gamboge.

The action of convolvuline upon the animal frame has been experimentally determined by various observers. The researches of Hagentorn appear to show that the pure glucoside is four times more powerful (as a drastic) than the soft resin. It rapidly produces pain in the belly, with liquid purging. Larger doses (3 1/2 gr.) have been known to kill a guinea-pig in three hours, the purging being followed by gastro-enteritis; and administered in considerable quantity, there can be no doubt that it is an active irritant poison. The researches of Bernatzik seem to indicate that when given internally, or by the stomach, it acts only in a local manner, affecting the alimentary canal. Hagentorn and Buchheim observed, on the other hand, that the subcutaneous injection of the convolvulinate of soda,1 in quantities exceeding 1 gram (15 to 16 grs.), produced, like jalapine, the symptoms of violent and fatal narcotic poisoning. It is remarkable that convolvuline appears to exert little or no irritant action upon the skin, the conjunctivae, or the nasal mucous membrane.

As a purgative, convolvuline is much more active than the substances derived from its partial decomposition. These are convolvulinic acid and convolvulin oil, which, together with sugar, are the characteristic products of the action of the mineral acids upon the glucoside. Neither convolvuline nor the substances just mentioned appear to be eliminated in the urine, nor (unless administered in enormous doses) to make their appearance in the faeces. Hence they are supposed to be absorbed, and then to be destroyed by combustion.

("1. Jalap is a hepatic stimulant of considerable power. It renders the bile more watery, but at the same time increases the secretion of biliary matter. 2. Its effect on the liver is, however, far less notable than its effects on the intestinal glands. Its hydragogue cathartic effects on the latter were fully manifested in these experiments." - R. & V. (Brit. Med. Jour., June 9, 1877.))

Therapeutic Action - Jalap was first known in England, as a medicinal substance, about the year 1610, though it is only of late that the source of the truest and best description of the drug has been accurately determined. Since the discovery of it by Europeans, it has probably come to be more generally employed as a cathartic than any other of vegetable origin.

In Dropsies. - Because of its hydragogue properties, jalap is especially useful in dropsies, over which it exerts a marked power, evacuating the effusions, especially when combined with bitartrate of potash or with calomel.

As a Vermifuge, jalap acts very well in cases of tapeworm and of lumbricoid worms. It is said to operate upon them as a poison, and certainly, in many instances, the worms have been found dead when expelled. When used for ascarides, this medicine should be given in combination with calomel.

Habitual Constipation, arising from dryness or scanty secretion, by the intestines, is overcome by jalap administered in a moderate dose, and also by the resin, the medicine being taken before rising in the morning, and followed, an hour afterwards, by a tumbler of cold water.

In inflammatory affections of the brain, or its membranes, when a purge is required, jalap often proves most valuable.

As a simple purgative for children, it may also be employed with the best results, in doses of from 1 to 5 grains.

Preparations and Dose. - Jalapa, gr. v. - xv. (.30 - 1.); Tinct. Jalapae, 3 ss. - jss. (2. - 6.); Resina Jalapae, gr. ij. - vj. (.12 - .36); Pulv. Jalap. Co., gr. x. - xxx. (.65 - 2.).

1 If treated with alkalies, convolvuline is converted into convolvulinic acid, a sub-stance analogous, as mentioned above, to jalapinic acid.