Osborne and Mendel (14) were unable to secure any growth with pea and bean proteins when these were carefully purified and fed as the principal source of nitrogen in the diet, the proteins of the legume seeds being supplemented only with the nitrogen of "protein-free milk." It has been shown in McCollum's laboratory that the protein mixture contained in the entire seed of the pea or bean is complete and can support fair growth when they serve as the sole source of protein in the diet. The other deficiencies in the seeds must, of course, be made good. Growth is possible only when the intake of protein in such diets is rather high (13). The proteins of these seeds are distinctly poorer in quality than are the combinations of proteins found in each of the cereal grains. Beans contain considerable amounts of hemicellu-loses which are not digestible but easily fermented in the intestine with the formation of gas and frequently cause flatulence.

A matter of great importance in comparing the relative values of the proteins of the legume seeds with those of meats, is the extent to which each supplies an abundance of those particular amino-acids which are not yielded in optimal amounts by the proteins of the cereal grains and tubers. The cereals form, in temperate climates, the greater fraction of our foods and supply most of the protein and energy of the diet. The milled products of these contain proteins of relatively low value and are deficient, without exception, in certain amino-acids. They may, when combined, mutually improve each other to a certain extent, but there are some essential amino-acids which are not abundant even in mixtures of several grains. In looking toward improvement of a dietary consisting largely of milled cereal products one of the important factors is the enhancement of the protein content. It is not so important to secure a high intake of protein as to have proteins of excellent quality. Relatively small additions of the right kind of protein greatly enhance the value of the proteins of cereals.