This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Pharm. Load. Jalapa Pbarm. Edinb. Macboacanna nigra. Jalap: the dried root ofthemirabilis peruviana or marvel-of-peru, firepan C. B. Convolvulus Jalapa Linn.(a) a plant with thick, sleshy radish-like roots; jointed stalks and branches; acuminated somewhat oval leaves set in pairs; and elegant, numerous, monopetalous, sunnel-shaped flowers, purple, yellow, white, or diverfery variegated, standing in double cups, of which the innermost incloses the flower and the outer surrounds its balls: each flower is followed by a wrinkled, roundish,
*(a) The later botanists are not perfectly agreed concerning the genus of the plant producing jalap. Linnaeus first made it a mirabilis; and Bergius now gives it as the mirabilis dicnotona Linn. from the resemblance between the root of that plant and the jalap of the shops.
Pentagonal umbilicated fruit, about the size of a pepper corn, including a white kernel. It is perennial, a native of the Weft Indies, and cultivated in our gardens on account of the beauty and duration of its odoriferous flowers, which open only during the night, and of which it produces continual successions from June or July till checked by frosts; at which time the roots, which do not endure our winter, are taken up, and preserved in sand till spring. Whether the roots produced here are equivalent in virtue to those which are brought from abroad, has not, that I know of been tried.
The officinal jalap roots come from the province of Xalapa in New Spain; in thin trans-verse dices, solid, hard, weighty, of a blackish colour on the outside or cortical part, internally of a dark greyish with several black circular striae: the hardest, darkest coloured, and those which have the most of these refinous veins, are the best. Slices of bryony root, which are said to be sometimes mixed with them, may be distin-guished by their whiter colour and less compact texture.
This root has scarcely any smell, and very little-taste upon the tongue: swallowed, it affects the throat with a slight kind of pungency and heat. Taken in doles of a scruple or half a dram, it proves an effectual and in general a safe purgative; very rarely occasioning any severe gripes or nausea, which too frequently accompany the other strong cathartics. Some have prohibited the use of this cathartic to children; probably on no very good foundation. Young children, from the laxity of their solids, and the lost lubricating quality of their food, generally bear these kinds of medicines better than adults, and adults of a spungy, lax, or weak habit, better than the rigid or robust. Few, if any, of the strong resinous purgatives are in either cafe more innocent than jalap.
Jalap root, digested in as much rectisied spirit as will cover it to the height of about four fingers, gives out greatest part of the resinous matter in which its activity resides, and tinges the menstruum of a yellowish brown colour. On inspissating the filtered tincture to about one half, and adding to the remainder a proper quantity of water, the liquor becomes milky, and on (landing deposites the pure resin. This preparation, given by itself, irritates and gripes violently, without proving considerably purgative: thoroughly triturated with testaceous or other powders, or with soap; or ground with almonds or powdered gum-arabic, and made into an emulsion with water; or dissolved in rectified spirit, and mixed with a proper quantity of syrup, that the solution may bear being diluted with watery liquors without precipitation; it purges, in doses of eight of ten grains, as effectually, and for the most part as mildly, as the jalap in substance.
The jalap remaining after sussicient digestion with spirit, has no cathartic virtue: boiled in water, it gives out a mucilaginous substance, which operates only by urine. Water applied at first takes up a portion of the resin along with the gum, and hence the watery decoction and extract prove weakly cathartic as well as diuretic: the root still retaining great part of its resin, so as to purge considerably. The resinous and gummy parts may be united into one extract, by first drawing a tincture from the powdered root with rectified spirit, then boiling the resi-duum in fresh quantities of water, evaporating the decoctions till they begin to grow thick, mixing in by degrees the tincture inspissated to a like thickness, and continuing a gentle heat till the whole is reduced to a due consistence. This extract may be taken by itself in doses of twelve grains or more: the gummy matter of the jalap being sufficient to divide the resin and prevent its too violent irritation.
The proportion of active matter differs greatly in different parcels of the jalap; sixteen ounces of some sorts yielding hardly two of resin, while the same quantity of others affords three or four. Hence the extracts of jalap appear preferable to the root in substance, not only on account of the dose being rendered smaller by the rejection of the woody parts, but likewife as being more uniform and certain in strength. Tinctures of jalap made in proof spirit are 'nearly similar in quality to the gummy resinous extract, this menstruum taking up both the resinous and gummy parts of the root: these preparations, made from different kinds of jalap, will vary in strength somewhat more than the solid extract or resin, but not so much as some have sus-pected, or as the roots in substance; for in the proportions usually employed, the proof spirit does not take up the whole of the virtue of any kind of jalap, and perhaps it does not extract much more from one kind than from another, provided the jalap be of moderate goodness. If three † or four ‡ ounces of jalap be digested in a pint of proof spirit, the residuum will still give out a portion of resinous matter to rectified spirit, and this resin will be in greater quantity in proportion as the root itself was the more resinous.
Extrattum jalapii Ph.
Land & Ed,
Tinct. jalap. † Ph. Ed. ‡ Ph. Land.