In this study the relative availability of inorganic and of organic iron in the diet of the normal infant has been investigated by means of a study of the iron balances over a long period. Interest in the problem was stimulated by the reports of Elvehjem and his colleagues,1 which indicated that in the case of rats only the inorganic portion of the dietary iron was utilized.
Until now practically all investigators interested in determining the "availability" of organic and inorganic or ionizable iron for hemoglobin synthesis have used anemic rats for their feeding experiments. Elvehjem and his co-workers1 found consistently that in the case of the anemic rat only the inorganic portion of the iron in the diet is utilized for the formation of hemoglobin. They found this to be true when a number of foods were given and the hemoglobin response was compared with that manifested