Knowledge of the energy requirements of infants and the energy content of their food is of fundamental importance in studying their rate of growth and in the treatment of nutritional disorders.
The ideal method for determining the energy transformation of infants is that of direct measurement of the heat eliminated and produced. This involves expensive, elaborate apparatus, and has been possible in but one laboratory, that of Prof. Graham Lusk in New York. Undoubtedly, the cost of this extremely accurate and delicate apparatus will preclude its ever being used extensively in hospitals.
The other method that we wish to take up is that of so-called "indirect calorimetry," i. e., a computation of the energy transformations from the gaseous exchange. It is possible to compute with considerable accuracy the energy transformations of the infant from the amount of carbon dioxid produced, and particularly from the amount of oxygen consumed. Unfortunately, direct