The many recent discoveries in the field of nutrition have necessitated a change in the methods of attacking nutritional problems. While for many years the chemical analysis of a feed was taken as the true index of its usefulness in a ration, we now know that feeds cont,.ining the same amount of protein, carbohydrates, and fat may differ widely in their physiological effect on the animal. Hart , McCollum, Steenbock, and Humphrey (1, 2) in an early study proved that growth and reproduction are seriously affected by limiting the ration of dairy heifers to the product of a single cereal plant. The heifers fed on the corn plant grew well, matured and showed early oestrus, and were physically strong in every respect. Those receiving the wheat ration grew at a fair rate until they reached 1000 pounds in weight, when growth ceased. They showed lack of vigor and evidence of physical weakness; even blindness finally resulted. They showed no oestrus. Similar, though not so marked, were the results obtained from feeding the oat ration. Later experiments bringing forth the accessory food factors and the difference in the quality of proteins have explained the reasons for many of the difficulties encountered in the studies of nutrition. The fact that these qualities and limitations of feeds cannot be determined by chemical analysis has opened a new field in the study of nutrition. Only by means of actual feeding trials of the many grains, alone and in combination, is it possible to deter° mine their physiological value; which determinations must be made before any constructive advance can be made toward the