All the legumes are covered with a tough skin, which is in itself indigestible, and which if not broken by the cooking process or by thorough mastication afterward, renders the entire seed liable to pass through the digestive tract undigested, since the digestive fluids cannot act upon the hard skin. Even when the skins are broken, if served with the pulp, much of the nutritive material of the legume is wasted, because it is impossible for the digestive processes to free it from the cellulose material of which the skins are composed. If, then, it be desirable to obtain from the legumes the largest amount of nutriment and in the most digestible form, they must be prepared in some manner so as to reject the skins. Persons unable to use the legumes when cooked in the ordinary way, usually experience no difficulty whatever in digesting them when divested of their skins. The hindrance which even the partially broken skins are to the complete digestion of the legume, is well illustrated by the personal experiments of Prof. Strümpell, a German scientist, who found that of beans boiled with the skins on he was able to digest only 60 per cent of the nitrogenous material they contained. When, however, he reduced the same quantity of beans to a fine powder previous to cooking, he was enabled to digest 91.8 per cent of it. The fact that the mature legumes are more digestible when prepared in some manner in which the skins are rejected, was doubtless understood in early times, for we find in a recipe of the fourteenth century, directions given "to dry legumes in an oven and remove the skins away before using them." The green legumes which are more like a succulent vegetable are easily digested with the skins on, if the hulls are broken before being swallowed. There are also some kinds of beans which, in their mature state, from having thinner skins, are more readily digested, as the Haricot variety.