Following the studies which led Osborne and Mendel (37) to conclude that the amino-acid lysin is not necessary for maintenance but is indispensable for growth, Osborne, Van Slyke, Leavenworth and Vinograd (39) made a very careful analysis of the principal proteins of the endosperm of wheat, maize and rice kernels, and found them to yield 1.58, 0.97 and 4.26 per cent, respectively, of the amino-acid lysin. They correlated these results with those of Thomas (47) secured in brief experiments upon himself and stated: "It is rather striking that the figures for the utilizability of these proteins correspond so closely with the lysin which they yield." The three-day type of digestion trial employed by Thomas, in which the factor of growth is not concerned, can be scarcely regarded as affording data comparable with the standards required in present-day experimental work.