42. Amylum.—Starch. Starch.

Fig. 20. Maranta starch (x 250) Fig. 21. Curcuma starch (x 350) Fig. 22. Wheat starch (x 250) Fig. 23. Rice starch (x 250) Fig. 24. Potato starch (x 250) Fig. 25. Corn starch (x 500)

The starch grains obtained from the fruit of Ze'a ma'ys Linné.

DESCRIPTION.—Usually in opaque, angular or columnar masses, easily pulverizable between the fingers, with a peculiar sound, into a fine white powder; odorless and tasteless. Under the microscope it is seen to be composed of small granules striated concentrically or excentrically around a nucleus or hilum. Insoluble in cold water, but with boiling water it forms a glutinous paste on cooling. Iodine is the test for starch, the characteristic blue color being produced when only a minute quantity of the latter is present.

Other starches—chiefly distinguished by the size and shape of the starch-granules as seen under the microscope:

Fig. 16. Spikelet of the Oat (Avena sativa). (a) AVENAE FARINAE.—Oatmeal. From Avena sativa Linné, probably native to Western Asia, but now a common field crop. A grayish-white, not uniform meal, containing the gluten and fragments of the integuments; bitterish. Demulcent and nutritive (due to the gluten contained).

(b) SAGO.—Pearl Sago. Globular, pearl-like grains, white or brownish, prepared from Metroxylon sagu, M. rumphii, and other species growing in the East India Islands.

Fig. 17. Triticum vulgare (Wheat). ](c) TAPIOCA.—Cassava Starch. Yielded by the rhizomes of Brazilian plants, Manihot utilissima and M. aipi, nat. ord. Euphorbiaceae. White and opaque, irregular lumps.

(d) TARO.—Taro Flour. A starch prepared from the corm of Colocasia esculenta Schott, the food (poi) of the natives in Hawaii and the West Indies. Recommended as a diet for dyspeptic and consumptive patients.

Starches from the underground parts of Triticum vulgare and Oryza sativa, Gramineae; Solanum tuberosum (potato starch), Solanaceae; Canna edulis, Maranta arundinacea, and Curcuma leucorrhiza, Scitamineae.

Fig. 281-286. Fig. 287-292. Powder.—Microscopical elements of: See Part iv, Chap. I, B.

CHEMICAL COMPOSITION.—Starch is the basis of that class of organic compounds termed carbohydrates. Its composition is C6H10O5. By hydrolysis it is converted into a gummy principle, dextrin, and glucose. Ferments convert it into alcohol and carbon dioxide—C6H10O5 = 2C2H5OH + 2CO2. Ash. Not more than 0.5 per cent.

ACTION AND USES.—Nutritive and demulcent.

Glyceritum Amyli (10 per cent.).
Dextrinum Album, N.F. (White dextrine should not yield more than 0.5 per cent. of ash.)

A Manual of Organic Materia Medica and Pharmacognosy, 1917, was written by Lucius E. Sayre, B.S. Ph. M.