The work reported in this paper is part of a study of the mechanism of anemia in infancy. The observations on the course of the changes in the hemoglobin and red cells in premature infants have been made with the purpose of studying the mechanism of the physiologic anemia of prematurity. All the babies comprising the study were in the wards of the Harriet Lane Home during the course of the determinations, and little attempt was made to follow them after they were discharged. Without a special mechanism in the clinic for insuring return visits, only those infants who are sick are returned for observation. For this reason many important practical questions will remain untouched in this work.
Methods.—Hemoglobin was determined by the Newcomer method, and the hemoglobin values were reported in grams per hundred cubic centimeters. The color index is based on the percentage of hemoglobin and