Certain physiological functions are directly dependent on the surface area of the body. The heat elimination, as first shown by Rubner, and the excretion of carbon dioxid and the consumption of oxygen are pari passu proportional to the extent of the body surface. The study of the heat production of infants by Rubner and Heubner and Niemann, and of the infants' respiratory exchange by Schlossman, allows one to compare the different infants under the varying conditions of experimentation. They have been studied while fasting and while taking diets of different compositions. Some of the children have been well, some moderately and some poorly nourished. Great care has been used and much labor has been expended in making the different forms of apparatus and the experiments accurate in all details. The metabolism of the children has been compared on the basis of their surface area. It is evident, therefore, that the