694 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



Description. Rhizome horizontal or oblique; cylindrical, more 

 or less curved and sometimes S-shaped; from 2 to 10 cm. in length 

 and 0.5 to 5 mm. in thickness, externally reddish- or purplish-brown, 

 somewhat annulate from scars of bud scales; upper surface having 

 short stem bases, lower and under portions with numerous long coarse 

 roots; fracture short; cortex grayish-white, about 0.075 mm. in 

 diameter and having a circle of resin canals, wood yellow about 0.300 

 mm. in width, pith white, large; odor distinct; taste pungent, bitter 

 and acrid. 



Roots grayish- or purplish-brown, unbranched, more or less 

 curved or frequently S-shaped, varying from 3 to 15 cm. in length 

 and 0.5 to 1 mm. in thickness; longitudinally or somewhat spirally 

 wrinkled; fracture short, somewhat tough. 



Inner Structure. Periderm consisting of a few layers of brownish 

 cork cells, and usually containing brownish amorphous masses; 

 cortex of inulin-containing parenchyma, having in the inner bark 

 an interrupted circle of large resin canals, which often contain a 

 yellowish-brown amorphous substance, either within the epithelial 

 cells or lining the cavity of the canal; fibrovascular bundles collateral, 

 consisting of narrow, hemispherical strands of leptome and paren- 

 chyma, and conical plates of xylem composed of numerous, narrow 

 tracheae and wood parenchyma and usually having a middle layer 

 of libriform; medullary rays broad, the cells containing inulin; 

 pith comprised of nearly spheroidal, inulin-containing parenchyma 

 cells, which are separated by large intercellular spaces. 



Constituents. From 0.5 to 1 per cent of a volatile oil, consisting 

 chiefly of the methyl ether of hydrothymoquinone and the phloryl 

 ester of isobutyric acid, also the methyl ether of a phlorol. In addi- 

 tion, Arnica rhizome contains an amorphous substance, arnicin; 

 about 10 per cent of inulin; tannic acid; gum; wax; several organic 

 acids; and ash from 8 to 15 per cent. 



Adulterants. The rhizome and roots of a number of other drugs 

 are sometimes substituted for arnica. These are distinguished by 

 the absence of resin canals. Consult Zornig, Arzneidrogen, Vol. I., 

 p. 444. 



Echinacea. The rhizome and roots of Brauneria angustifolia 

 and B. pallida (Fam. Composite), perennial herbs; the former being 

 the purple cone-flower of the southwestern United States and the 

 latter occurring throughout the central United States and extensively 

 cultivated, and known as the cone-flower. The rhizomes are col- 

 lected from well-developed plants in the autumn and carefully 

 dried. 



