This is the most important seed grain used as food by all western peoples, and is second only to rice in respect to the quantity used as food for man. The latter is in greatest favor among peoples of the eastern hemisphere. The dietary properties of the wheat kernel have been described in Chapter II (A Biological Method For The Analysis Of A Foodstuff. 17. Mccollum'S Experiments Not Verified By Osborne And Mendel) in connection with the development of the biological method for the analysis of a food-stuff. The proteins of this grain are about as efficient for the promotion of growth as are the same amounts of protein from milk or eggs, or of certain combinations of two or more foods whose proteins are so constituted as to supplement each other's deficiencies. There is no cereal grain yet adequately studied which has been found to contain proteins superior to those of wheat. Its prominent place in the diet of mankind is, therefore, justified by the results of experiments on animals. When the wheat kernel is satisfactorily supplemented with respect to all other dietary factors, its proteins have proven satisfactory for the promotion of ordinary growth and the maintenance of good nutrition over a considerable fraction of the normal span of life of the rat, even when the protein content of the food mixture did not exceed 9 per cent of its calorific value. This is illustrated by the records in Chart 4. The results of feeding diets in which wheat was the sole source of protein have not been uniformly successful, and it appears that some samples of wheat are superior to others. It is well known that the quality of the proteins vary markedly in different samples of wheat, with respect to their glutinous property so important in bread-making, and the reason for this seems not to have been satisfactorily explained. It may be due in part at least to variability in the proportions among the several individual proteins in the seed. If this is true, it would account for such inequalities in nutritional value as have been observed.

Wheat is too poor in calcium to meet the needs of the growing rat. The average content of this element per 100 grams of this cereal is about 0.041 gram. The optimum content of calcium for the growing rat is not far from 0.64 per cent of the food mixture. Phosphorus, sodium, chlorin and iodin are also present in the wheat kernel in amounts too low to support normal nutrition in this species. The content of mineral elements in any plant product is subject to some variation, depending upon several factors, chief among which is the content of each of the several inorganic ions in the soil. The amount of water transpired during the growth of the plant is also a controlling factor (1).

In general the entire wheat kernel is not used as human food, and the grain is fed to animals only under exceptional circumstances, because it is usually more valuable for the manufacture of flour. Bread made from whole wheat is dark in color, but has a flavor which is very agreeable. Whole wheat flour does not possess very good keeping qualities. The germ of the seed (wheat embryo) is rich in oil, and this tends to become rancid when the kernel is broken by milling. The rancidity spoils the flavor of the flour. Furthermore, the insects which infest cereals select the germ as the site for the deposition of their eggs, so that whole wheat flour contains many more insect eggs than does flour free from germ.