(From Chalapa, or Xalapa, a city in New Spain). Jalap. Gialappa, chalapa, xalapa, mecoca-fiana nigra, convolvulus Americanus, bryonia Peruviana. There is said to be a third species of jalap called mutalista, by the Indians mathalistic.
This plant is a native of Mexico, and found near the city of Xalapa, from whence its name is derived; but it has since been discovered near Vera Cruz and on the south of Florida. It was carried by Michaux to the botanic garden in South Carolina, where an old root was found, weighing, when fresh, above fifty pounds. (Annales du Musaeum National, vol. ii.) It was at first referred by Linnaeus to the genus mirabilis, with the trivial name of jalapa; but observing the size and shape of the root of the m. longiflora, he was inclined (Amoe-nitates Academicae, vol. vii. p. 308.) to think them the same; for no botanist had yet described the flowers of the officinal root. Bergius, on trial, found, however, that neither of these species was purgative, but that the root of the mirabilis dichotoma was so. To this plant then he referred the jalap; and, on his authority, the compilers of the Swedish Pharmacopoeia did the same. Houston seems to have first shown that it was a convolvulus; and in this he was followed by Sir Hans Sloane, Miller, and at last Linnaeus himself in the Mantissa of the System of Nature. It is, therefore, the convolvulus jalapa of the Mantissa and of Wildenow (vol. i. p. 860); but the only figure which shows the parts of fructification complete is in the second volume of the Annales of the National Museum. The author (Desfontaines), from its simple sloping stigma, suspects that it rather belongs to the genus ipomaea.
The roots are brought from New Spain in transverse slices; they are solid, hard, weighty, of a blackish or dark brown colour on the cortical part, internally of a dark greyish colour, with several black circular striae.
The hardest, darkest, and those pieces which have the most numerous resinous veins; those that break most compact, shining, and that burn readily at the flame of a candle, are preferred. Worms rarely touch the resinous part: so, when the resin is only wanted, the worm eaten are not inferior.
Pieces of briony root are sometimes mixed with the jalap, but are easily distinguished by their paler colour and less compact texture, and by their not readily burning at the flame of a candle.
Jalap hath scarcely any smell, and little taste; but when swallowed it affects the throat with a slight pungency and heat, occasioning a spitting. In doses from ten grains to half a drachm it is an effectual cathartic, but gripes and nauseates less than the generality of purging medicines in use. For children in general, and adults of a leucophlegmatic habit, it is peculiarly proper, though it is not unsuitable to constitutions of a different kind. It is diuretic as well as purgative, and consequently preferred in dropsies. Lewis thinks that the gummy part promotes a flow of urine, while the resin purges; but, from experiments made with this view, we did not find the distinction correct.
If well triturated with crystals of tartar before exhibition, it will operate, it is said, in smaller doses than when taken by itself, and without griping. Rubbed with hard sugar, it becomes a safe medicine for children; joined with calomel, in large doses, it is rendered one of the most powerful purgatives, either as a hydro-gogue or anthelmintic; and, from its general efficacy in dropsies, was called panacea hydropicorum. The dose of the simple powder is from i. to Э ij. The compound powder may be double the quantity. It generally requires no corrector, but a little spice, or a few drops of some warm oil.
Resina jalapii. Resin of jalap. - Take any quantity of powdered jalap root; pour upon it so much rectified spirit of wine as will cover it to the height of four lingers, and digest them in a sand heat; filter the tincture through paper; put it into a glass cucurbit, and distil off one half of the spirit; add to the remainder a proper quantity of water, and the resin will precipitate; divide it into little cakes, and dry with a gentle heat. This has no place in the Pharm. Lond. 1788; but the extract is directed to be made like the resinous extract of bark.
It is a pure resin: but its insolubility in any aqueous fluid forbids its use, except it is previously triturated with an alkaline salt, gum, sugar, or a similar intermede. If thus managed, a dose from gr. v. to x. operates with sufficient ease and efficacy.
The jalap which remains after this resin is extracted, gives out, by boiling in water, a mucilaginous sub-sbtance, which is said to operate by urine, but not in any degree by stool. But this is asserted without foundation.
From sixteen ounces of good jalap Neumann obtained v. and Э iv. of pure resin; but in the shops it is frequently adulterated; and the methods of imitating it are so various, as to elude every known method of detecting the fallacy.
The advantage of the extract consists in the equality of its strength; for some of the roots afford only ij. while others afford v. of the resin in a pound. But, except for the convenience of form, the tincture, with proof spirit, will answer every purpose proposed by the gummy resinous extract of the college, which may be given from Э ss. to Э i.
Tincture of jalap is made by digesting eight ounces of powdered jalap in two pounds of proof spirit, with a moderate heat for eight days, then straining the tincture. The dose is from 3 i to ss.; mixed with syrup, it may be given to children with the greatest safety. This is the purgative said to be given by the inocula-tors who received their instructions from Sutton (Cul-len's Materia Medica); and sufficiently certain in point of strength, as the menstruum does not extract the whole virtue of any kind of jalap. See Neumann's Chemical Works; Lewis's Materia Medica.
Jalapa alba. See Mechoacana alba.