Buckner, Nollau and Kastle (48) interpreted Osborne and Mendel's data as showing that "lysin is primarily responsible for the stimulation of growth." They apparently regarded the planning of farm rations so as to insure a sufficient amount of this amino-acid, as one of the specific agricultural problems of practical importance. These investigators fed chicks such complex mixtures as wheat, wheat bran, sunflower seed, hemp seed and skim milk, and contrasted the growth and well-being of these chicks with others restricted to barley, rice, hominy, oats and gluten flour. The former were well nourished and grew in a normal manner while the latter were stunted and miserable-looking creatures. Buckner, Nollau and Kastle interpreted their results as being due to "differences in the amino-acid content of the two rations and in all probability to differences in the lysin content."

It will be observed that the poor ration used in the feeding of chicks was limited to cereal grains and their by-products. One of the most important generalizations that can be made as the result of modern nutrition investigations is that it is not possible to secure a diet composed entirely of seeds of plants which will promote good nutrition over any considerable period. The diet in question was, it is true, poor in the amino-acid lysin, but its mineral content was deficient in certain elements, notably calcium, phosphorus, sodium and chlorin, so that growth was prevented in their chicks, even if the proteins had been of better quality. Furthermore, this diet was very deficient in the substance fat-soluble A, without which prolonged well-being is not possible. It contained but a trace of the anti-scorbutic substance, which may have been of some importance in preventing the development of the chicks. The good diet on the other hand was composed in great part of whole seeds, the germ of which improved the quality of the entire mixture of vegetable components to an important degree. The bran was important as a source of mineral salts, since the cortical layer of seeds is especially the region in which these occur in the seed. When in addition to these differences between the two diets, the presence of skim milk in the successful one is considered, it becomes apparent that the two diets were in no sense comparable even in regard to factors other than the lysin content. It can confidently be predicted that a liberal addition of lysin to their poor diet, or indeed, a liberal addition of all the essential digestion products of protein in the form of a purified protein such as casein, would not have changed the outcome of their experiment.

In a later study Osborne and Mendel (49) employed maize gluten, which contains about 1.0 per cent of lysin, supplemented with "protein-free milk" sufficient to furnish 1.33 per cent of the total nitrogen of the food mixture, as the source of protein for growing chicks. They compared the growth obtained with this protein mixture with that obtained with rations similar in their make-up except that the maize-gluten nitrogen and "protein-free milk" nitrogen was supplemented with lactalbumin or cottonseed flour. The latter supplements are known to be rich in lysin. The results were interpreted as confirming the conclusions of Buckner, Nollau and Kastle in respect to the effect of foods high and low in lysin on the growth of chicks.

From the standpoint of practical nutrition these experimental studies all tended to focus attention upon lysin as an amino-acid of more importance than other indispensable digestion products of proteins, because of the assumption that it is relatively less abundant in proteins of the cereal grains, as wheat, maize, and others.