400 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



and crotonalbumin; the alkaloid ricinine, also found in Ricinus; 

 several ferments; ash from 4 to 6 per cent. 



Transvaal Croton Bark. The bark of the tree, Croton Gubouga 

 S. Moore, a species widely spread in Nyasaland, Rhodesia and Por- 

 tuguese East Africa. In external appearance the bark is 2 to 3 mm. 

 thick, generally gray in color, with corky warts or longitudinal bands 

 of cork. The bark possesses a persistently acrid, somewhat numbing 

 taste. Microscopically, bast fibers, single and in groups, much 

 thickened and distinctly striate, sclerenchyma cells, abundant; cal- 

 cium oxalate crystals in prisms and rosettes numerous; a few small 

 starch grains and small oil drops occur in the parenchyma and in the 

 longitudinal section some elongated cells with the inner lamellae 

 of the walls suberized and containing yellowish granular secretion. 

 Petroleum spirit yields 2.54 per cent of thick fatty oil, exceedingly 

 acrid in taste. Alcohol yields 2.71 per cent of an acrid extractive. 

 Alcohol of 50 per cent strength apparently extracts the drug. Green- 

 ish, Pharm. Jour., 1918, 101, p. 289. 



Cassava Starch. AMYLUM MANIHOT, PARA OR BRAZILIAN 

 ARROWROOT. The starch grains obtained from the thickened roots 

 of the bitter cassava (Manihot utilissima) and the sweet cassava 

 (Manihot palmata Aipi), perennial herbs belonging to the Euphor- 

 biaceae, natives of South America and extensively cultivated in the 

 West Indies, tropical South America and to some extent in Florida 

 and other southern States. The plant is very easily grown and pro- 

 duces very large roots, weighing sometimes 5 K. At harvest time the 

 roots are dug, washed, cut and scraped, whereby the starch grains 

 are released and finally obtained by methods, similar to those em- 

 ployed in the manufacture of potato starch. The starch is obtained 

 in large quantities in Brazil from the root of the bitter cassava, 

 the hydrocyanic acid being eliminated during the process of wash- 

 ing and drying. In Florida considerable starch is made from the 

 sweet cassava. - As this starch is sold very often at a price below 

 even that of corn starch it is used to some extent in the arts, chiefly 

 as a sizing for cotton fabrics. 



Cassava starch occurs as a fine mobile powder, the grains being 

 mostly single or 2- to 8-compound, the individual grains being some- 

 what plano-convex or bell-shaped, varying from 0.005 to 0.030 mm. 

 in diameter and having a distinct central circular or radiating cleft 

 (Fig. 20). 



Tapioca is formed by heating the cassava starch while it still 

 contains a maximum degree of moisture. It is heated upon iron 

 plates first at a low temperature, which is gradually increased until 



