THE CHANGES in composition which the blood of infants undergoes during the first year of life have been extensively investigated. The excellent reviews of previous studies, included in the reports by Mackay (1931)1 and Faxén (1936-1937),2 obviate the necessity of a survey of the literature in the present paper. These reviews point out the many factors which have been suggested as influencing the blood picture and suggest that hypochromic anemia may be a common occurrence in young infants. Considerable doubt remains, in consequence, as to what constitutes the normal blood picture in infants and what may be considered as the limits of physiological variation.
The present study was undertaken for the purpose of helping to establish normal hematologic standards for infants residing in Minnesota and of investigating the influence of certain factors on the blood picture.
The study was conducted at two well-baby clinics in St. Paul