One of the three facts which stood out prominently in my consideration of the types of diets which had succeeded in human experience and with animals, was that certain peoples and many animals were thriving on diets in which the leaves of plants were important articles of food. Thus the grazing animals may live throughout their lives on grass or other palatable forage plants. All the animals of the cattle, horse, sheep, goat, deer and other types, in their early history had no grain, and subsisted entirely upon grass. The bison never had anything else throughout life. The giraffe feeds upon the leaves of trees and shrubs. This idea seemed very fertile, when one considered that swine had, in our experimental trials, failed so signally in their nutrition when confined to a diet of a cereal grain or mixture of several cereals such as wheat, maize or oats. On reflection, it naturally occurred to me to consider the function of the seed as contrasted with the leaf. The former is a storage tissue, formed to supply the plantlet which develops during germination, with sufficient nutriment to enable it to form a root and leaf system. After this stage it is independent of further aid, and can secure everything it needs from the soil and air. The nutritive needs of a plant are very different from those of an animal. The plant can synthesize its proteins and carbohydrates as well as all the other components of its complex structure. The animal must secure these ready formed or it will perish. The leaf, on the other hand, is the laboratory of the plant. It is here that the numerous complex organic syntheses take place. We may reasonably assume that there are structures and chemical substances here which would not be found, at least in abundance in a seed. Were not the dietary properties of the leaf superior to those of the seed? Experimental trials showed clearly that this surmise was correct.