Both cassava and tapioca are very rich in starch, containing from eighty-five to ninety per cent. They are made from the fleshy roots of two species of the tropical genus Manihot; one the "bitter," and the other the "sweet" cassava. The bitter cassava, when robbed by heat of its poisonous qualities, makes cassava flour and tapioca.
In sick diet we are only concerned with tapioca in the fine granular form. Larger pieces require long soaking and careful cooking to be digestible. Pearled tapioca (tapioca made into small round grains the size of a pea) may be added to soup for the well, but for the sick fine granulated tapioca alone should be used.