This report is part of a study which is now being carried on in the pediatric department on the problem of the anemias of infancy and childhood. Many studies have been made in this field but most of the work so far done has reference mainly to the blood picture, studies relating to the differential count of the white blood cells, the study of the red blood cells, their number and fragility and to the percentage of hemoglobin; in many instances the postmortem findings are added to these studies of the cells and hemoglobin. All these studies are valuable and have their place in the problem of the anemias but so far they have led to little more than an unsatisfactory classification of the anemias. Even as regards classification there is much confusion and very little has been ascertained as to the etiology of the various anemias which occur so