Iron-containing granules (40 to 100 A in diameter), in groups or isolated, are present in normal erythroblasts, normoblasts, reticulocytes, and certain pathological erythrocytes. Similar granules are present in macrophages and have been noted in the stroma of erythrocytes following phagocytosis and hemolysis by macrophages. Incorporation of the granules from the macrophage into erythroblasts is presented as a process similar to pinocytosis. The presence of the iron-containing granules within the erythroid cells parallels hemoglobin synthesis.

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