An important aspect of studies of nutrition in animals has been the observation of the effects of different diets on the rate of growth. The effects of reduction or increase of various dietary components on the growth of animals which mature rapidly are easily recognized. This approach to the study of human nutrition has been discouraging, for a number of reasons which will be discussed more fully, but primarily because the progress of human growth is relatively slow and the developmental period covers a long span of time.
Many of the present uncertainties as to what constitute optimum diets for children at different ages result from the lack of accurate information as to what effects differences in the consumption of various food substances have on the progress of growth and development. It is well recognized that under conditions of extreme depletion and in the presence of pathologic evidences of certain