_Wheat flour_ enters largely into the diet of every family. In producing it the outer coating of the wheat kernel is removed, thus throwing into the milling offals that part of the kernel which is most heavily charged with mineral ingredients and vitamins. The proportion of digestible proteins in white flour is not less than in whole wheat flour, as is so often claimed, but because the latter is richer in mineral ingredients its use is recommended. Bread is readily digestible; white bread digests more rapidly than brown or black; and crackers more rapidly than either. _Rice_ is another cereal of great economic importance. As a food for invalids it possesses a high value on account of its digestibility, especially in intestinal diseases. Ordinarily polished rice contains only 0.5 per cent. of cellulose, and almost all of the substance of the grain is absorbed. There is a perfect analogy between the well-known relation of the polishing of rice to its nutritive value, and the milling of wheat and corn to the nutritive value of wheat, flour, and cornmeal; that is, it loses the mineral ingredients and vitamins. _Potatoes._—In European countries potatoes rank next to bread; this arises from the ease of their digestion. From 92 to 95 per cent. of the starch is absorbed, but there is a loss of 23 per cent. of the protein. The manner of preparation of vegetable foods determines the proportion of loss. When potatoes are baked or boiled in the skins the loss is negligible. The greatest amount of loss occurs when the skins are removed, the potatoes then allowed to soak in cold water, and placed in cold water to boil. The potatoes should be pared just before cooking, and the water should be boiling hard before they are put in. Mealy potatoes digest more rapidly than waxy ones, and mashed quicker than unmashed. Oatmeal, barley meal, and other cereals which are not ground very fine do not digest so easily as wheat flour, but much depends on the mode of cooking. When oatmeal-gruel is consumed with a sufficient amount of milk it forms a complete diet. Nuts are valuable as a source of protein and fat, but they are rather difficult of digestion. _Fats._—As a rule, children do not thrive whose diet is deficient in fats, and even adults are prone to tuberculosis and nervous diseases when fat in the body is deficient. Cheese is one of the most indigestible of foods. All fried foods are highly indigestible because the fat envelope of the foods has to be melted off before the gastric juice can act on the food substance itself. Pastry is also very indigestible. Of the vegetables, beans, while highly nutritious, are exceedingly difficult of digestion; also boiled cabbage, cauliflower, hot breads, iced drinks, ice-cream, and water-ices. =The Relation of Diet to Various Conditions of Life.=—The chief factors influencing bodily needs are age, height, weight, occupation, idiosyncrasies, and atmospheric conditions.