R.: Studies in iron transportation and metabolism. II. The mechanism of iron transportation: its significance in iroi utilization in anemic states of varied etiology

A growing interest in the mechanism by which iron is transported in the blood stream has been stimulated by the desire to understand more fully this essential phase of iron metabolism in the mammalian body. With the clarification of this important detail a more complete understanding of normal erythropoiesis and of the iron de-ficiency states may be anticipated. Despite a wide variety of observations reported in the literature, an entirely satisfactory and ac-ceptable experimental definition of the manner in which iron transportation is effected has not as yet been presented. A. B. Macallum (1), Ehrlich and Lazarus (2), and Proescher and Arkush (3) observed that histologically many erythrocytes give an iron reaction. They assumed, therefore, that free iron, not identified with the hemoglobin molecule, is present in at least a portion of the red cells. Macallum postulated that iron is trans-ported by the etrythrocytes, and Proescher and Arkush further suggested that this may be ac-complished through a loose combination with the lecithin of the erythrocyte corpuscular membrane. Other investigators (4 to 14) have studied the iron content of plasma and serum in the hope that some light might be shed on this problem of mineral transport, but their researches have not yielded conclusive information. Barkan (15, a and b) has assigned to the " easily split-off " blood iron fraction the function of iron trans-portation and considers plasma iron as the me-dium of exchange between the tissues and " easil