The studies of the size and hemoglobin content of red blood cells which have been made by many investigators in recent years have yielded much valuable information concerning the normal physiology of the blood cells and their changes in different types of anemia.1 While such studies have been concerned for the most part with adult subjects, those dealing with infants and children, although less extensive, have shown clearly that in both normal and anemic infants the red cells undergo remarkable changes during the early years of life. The literature of this phase of the subject has been adequately reviewed in this journal by Osgood and Baker,2 Mugrage and Andresen3 and Guest and Brown.4
A few examples of data obtained on samples of blood from normal and from anemic infants were presented in the first paper of this series.4 These examples were selected to demonstrate the