This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Arrowroot is derived from the rhizomata or root stocks of several kinds of tropical plants grown in both the East and West Indies. The roots are washed, reduced to a pulp, strained, dried, and pulverised into a very fine starchy flour. The best flour is made from the Maranta arundinacea. It is obtainable in market in the form of a fine white powder, and consists of exceptionally pure starch, the granules of which are small and friable. It has a very bland, insipid taste, and it is as digestible or more so when cooked than any other starch which is used in making gruel or jellies for invalids. In the form of a jelly it keeps longer without souring than do many other forms of starchy food, such as the potato; and in bad cases of dyspepsia, when much gastric irritation exists, it often constitutes a serviceable article of diet. Arrowroot is sometimes fed to young infants, but it is unwholesome for them, and ferments in the stomach.
Tous-les-mois is a starch derived from a West Indian tuber by maceration, straining, washing, and drying. It is used for the same purpose as arrowroot. Its granules are the largest of any of the food starches, but they are quite digestible and nutritious for invalids.
Salep is a starchy food which is obtained from the tubercles of certain Oriental orchids. It is a mixture of starch and mucilage which makes a useful demulcent drink.