Iron metabolism and haemoglobin formation in the embryonated hen egg. 2. Some observations on the embryonic blood supply

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Abstract
Total and non-heme Fe were determined in the embryo and the remaining portions of fertile eggs frozen and dissected after incubation for various periods. Heme Fe in the embryo body increases in such a way that the logarithm of the amt. present is directly proportional to the logarithm of the wet wt. This relationship holds until the last 2 or 3 days of incubation. The quantity present is about 10 [mu]g. at embryo wt. 1 [mu]g., 300 [mu]g. at 20 g., and 600-750 [mu]g. at 30-35 g. Heme Fe in the membranes increases to a max. of 200-300 [mu]g. at embryo wt. 16-19 g., and then decreases sharply. While the embryo increases in wt. from 3 to 18 g., the proportion of the membrane heme in the chorioallantois remains about 40%. The proportion of the total heme which is present in all the membranes decreases from 75% at embryo weight 2 g. to 50% at 14 g. and 10% at 30-35 g. A comparison is made between these figures and the state of affairs in the uterus of the pregnant sheep, as described by Barcroft (1946). Evidence is presented that towards the end of incubation a quantity of heme is destroyed which is broadly equivalent to that disappearing from the membranes. The liberated Fe accumulates in the embryo, presumably as a store.

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