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.
Though formerly recognized by all the British Colleges, this has been omitted in the British Pharmacopoeia of 1864. it is obtained from the root or rhizome of Maranta arundinacea, and other species of Maranta, herbaceous perennials, growing in the West indies, where, as well as in our own southernmost States, they are cultivated for the sake of this product. it is prepared by agitating the bruised roots with water, which holds the separated starch in suspension, and which, being strained, and permitted to stand, deposits the powder. This being washed and dried in the sun, constitutes the arrow-root of the shops. it is in the form of a fine white powder, or easily pulverized lumps, very light, and possessed of all the properties of starch, of which it is a very pure specimen. it should be free from smell or taste.
Arrow-root is used more for food for the sick than as a demulcent, though, while performing the former office, it also frequently does good incidentally in the latter capacity. its perfectly bland, and moderately nutritive properties, adapt it to febrile and inflammatory diseases, especially in approaching convalescence, and in irritated states of the stomach and bowels. it is used in infantile eases, and not unfrequently as a digestible article of diet for healthy children after weaning, or when insufficient milk is afforded by the nurse. A tablespoonful is sufficient for a pint of water. The powder should first be mixed with a little cold water, and afterwards stirred with boiling hot water. On cooling it forms a whitish gelatinous solution. if the arrow-root is added largely, a solid jelly-like mass results. The powder is often also boiled with milk, or with a mixture of milk and water, as a diet for children and the sick, when support is required, as in typhoid cases, and in convalescence. Sugar or molasses, lemon-juice, or, if not contraindicated, a little wine may be added to the pure aqueous solution, to improve its flavour.
Several other forms of starch, procured from different sources, and having more or less of the appearance, and sometimes bearing the name of arrow-root, have been substituted for it; but it is rare to find any one so pure, and so free from all unpleasant taste. Among these may be mentioned purified potato-starch; a preparation made in the South Sea islands from a species of Tacca, called the Tacca arrow-root; and the tous-les-mois or carina, from an undetermined species of Canna, supposed to be C. coccinea, growing in the West indies. The last mentioned is a very fine variety of starch, and may be employed for the same purposes, and in the same manner as arrow-root.