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Oxygen dissociation curves of the bloods of pregnant sheep, fetal and newborn lambs have been prepared at plasma hydrogen-ion concentrations in the physiological range. At pH 7 4, the fetal blood was half saturated at about 16-0 mm.Hg oxygen pressure. The maternal oxygen dissociation curves of the blood of different animals showed variability in their positions; half saturation occurred at values of oxygen pressure ranging from 316 to 37-5 mm. Hg. The curves of bloods of newborn lambs had positions intermediate between fetal and adult types.

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has suggested that phagocytes might re-utilize the DNA from a single cell; this would result in delayed labeling of the phagocyte (see "Homeostatic Mechanisms," Brookhaven Symposia Biol., 1957). 8 S. R. Pelc, Nature, 160, 749, 1947. 9 The data presented in this report were obtained during part of an investigation' directed primarily to study the "forces" that determine the net transfer of water across the placenta from the maternal to the fetal blood and the mechanisms that regulate the water content of the fetus and the surrounding cavities. To learn whether electro-osmotic phenomena operate in the process of transfer of water across the placenta, we have proceeded to determine whether or not any difference in electric potential exists across the barrier that separates the maternal from the fetal blood.The animals used for the experiments were goats (duration of pregnancy 145-47 days), bred on known dates. The heparinized mother was under spinal anesthesia (Pontocain) and received, in addition, a light dose of thiopental sodium (Pentothal) VOL. 44, 1958 483

No abstract