This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
The British Pharmacopoeia has omitted this with the two preceding articles. it is the product of Janipha Manihot, the mandioca or cassava plant, a shrubby plant, indigenous in S. America, where, especially in Brazil, it is largely cultivated for food. There are two varieties, one the sweet, the other the bitter cassava, of which the latter, though its root is poisonous in the recent state, is most largely cultivated on account of its productiveness. By exposure to heat, however, the poisonous properties, which have been ascribed to hydrocyanic acid, are entirely dissipated, and the root becomes perfectly safe. it is used in various ways, and enters largely into the diet of the people. Tapioca is obtained by expressing the root. The liquid thus obtained, being allowed to stand, deposits starch, which is washed, and afterwards prepared by exposure to heat.
It is in irregular, very rough, hard, white grains, inodorous, of a very feeble taste, and with all the properties of starch; being, however, slightly soluble in cold water, in consequence of the heat employed in its preparation.