JALAPA 



365 



HABITAT. Mexico; now successfully cultivated in India. 



DESCRIPTION OF DRUG. A compact, heavy, hard, pear-shaped tuber, 

 varying in size, but never larger than the fist; the larger ones are 

 longitudinally incised to facilitate the drying, which is done over 

 the hearths of the Indian huts, hence externally brown, smoky, 

 more or less wrinkled, covered with thick, round warts of a some- 

 what lighter color; internally gray to dark brown; fracture horny 

 and resinous; odor peculiar, smoky, partly due to the manner of 

 drying; taste starchy, afterward slightly acrid. Powdered jalap is 

 yellowish-gray, and when inhaled causes sneezing and coughing. 



STRUCTURE. Cortical layer thin, with a dense circle of resin cells near 

 the cambium line; interior composed chiefly of parenchymatous 



FIG. 210. Jalap tuber. (Photograph.) FIG. 



an. Jalap Cross-section of tuber. (2 

 diam.) (Photograph.) 



tissue containing starch and calcium oxalate, arranged in which are 

 concentric zones of resin cells, the broader, darker, alternate zones 

 being formed by a closer packing of the cells; medullary rays small, 

 but plainly visible. The false jalaps which frequently adulterate the 

 drug in market may usually be detected by the difference in internal 

 structure. 



ADULTERATIONS. Immature roots, roots partially deprived of resin by 

 treatment with alcohol. These are sticky, internally darker than the 

 genuine and other species of Ipomcea. 

 Powder. Characteristic elements: See Part iv, Chap. I, B. 



CONSTITUENTS. Besides starch, calcium oxalate, etc., jalap contains a 

 resinous substance which consists of two portions, a soft resin, jalapin, 

 soluble in ether, and a hard resin, constituting nine-tenths of the 



