NON-POISONOUS DRUGS 165 
the inner bark of our slippery elm and the closely similar 
English elm (Fig. 159) is due to the large amount of a muci- 
laginous carbohydrate which it contains. The pith of sassa- 
fras (Fig. 160) yields to hot water a similar mucilage. 
Fig. 157.—Tragacanth Shrub (Astragalus gummifer, Pulse Family, Legumi- 
nose). A, flowering branch. B, leaf from which the leaflets have dis- 
appeared, leaving only the stiff thorn-like ‘‘rachis’” and the toothed 
‘“stipules.”’ C, flower. (Taubert.)—A shrub 30-60 cm. tall; flowers 
yellow; pod, small, one-seeded. Native home, Southwestern Asia. 
The jelly-like constituent of the lichen called Iceland moss 
(Fig. 161) is a carbohydrate known as lichenin or lichen- 
starch (CysH2 01). It is insoluble in cold water but  be- 
comes dissolved upon boiling, and forms a jelly when cooled. 
Lichenin is almost if not quite identical with the gelatinous 
constituent of carrageen or Irish moss (Fig. 118) which we 
have already studied. The chief remedial constituent found 
