ROOTS AND RHIZOMES. 
131 
JALAPA (Jalap). 
The tuberous root or tubercle of Exogonium Purga 
(Fam. Convolvulaceie), a perennial twining herb, native 
of the eastern slopes of the Mexican Andes, and culti- 
vated in Jamaica and India. The roots are collected 
in the fall and dried by artificial means, the larger 
ones being first cut into longitudinal pieces. Mexico 
furnishes the principal part of the commercial supply, 
which is exported from Vera Cruz. 
Description. — Fusiform, irregularly ovoid or pyri- 
form, upper end more or less rounded, lower end 
obtuse or slightly acuminate; 3 to 8 cm. long, 1 to 5 
cm. in diameter; externally dark brown, deeply and 
irregularly furrowed longitudinally, otherwise nearly 
smooth or wrinkled, with numerous lenticels 2 to 4 
mm. long and few circular rootlet scars ; fracture horny 
and resinous ; internally dark brown and marked 
by more or less distinct, secondary, concentric cam- 
bium zones ; odor fruity ; taste starchy and slightly 
acrid. 
Tubercles which have a specific gravity less than 
T275 and are white internally should be rejected. 
Constituents. — Resin 7 to 20 per cent., 90 per cent, 
of which consists of a glucoside, jalapurgin (convol- 
vulin), which is insoluble in ether and is the more 
active constituent, and jalapin which is soluble in 
ether and resembles scammonin ; jalap also contains 
calcium oxalate, starch, gum and sugar. 
Allied Plants. — Ipomsea simulans, indigenous to the 
eastern slope of the Mexican Andes, yields the Tam- 
pico jalap, which is more or less uniform in thickness, 
somewhat tortuous, and without any lenticels ; it con- 
tains about 10 per cent, of resin, which is completely 
soluble in ether and resembles scammonin. 
