Summary. The interactions of oestriol and progesterone were studied in a series of assays for oestrogenic and progestational activities, and the responses were compared with data on progesterone-oestrone combina¬ tions in the same tests. The vaginal effects of these two oestrogens do not seem to differ, whereas the interactions of oestriol and progesterone are quite different from the interactions of oestrone and progesterone when uterine end-points are considered. Since oestriol is the dominant aromatic steroid excreted during pregnancy and the luteal phase of the menstrual cycle, we feel that explanations for many unsolved problems of luteal-phase and pregnancy physiology may reside in these interactions.

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ESTROGEN ANTAGONISTS 53 7 sera as described by Chang( 1!11) has not been a problem. We have found that only one of 23 human serum pools was toxic to FL cells.In preliminary experiments with FL and HeLa cells the FL cells have not produced tumors in treated rats using a technic3 in which HeLa cells produced significant tumors. More work is needed however before a conclusion can be established. Summary.A strain of human cells derived from a normal amniotic membrane has been cultivated in serial passage for 8 months in 30 transfers. This cell line was developed by trypsinization of the primary source and cultivated in a medium without embryo extract. The appearance of the cell has been epithelial-like a t all stages of cultivation. Growth characteristics in media containing human serum or animal sera are reported. The cell strain has been grown in large scale.

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175the chick comb in animals not treated with androgen were significnatly reduced by administration of this compound. A-norprogesterone is not androgenic, estrogenic, anti-estrogenic, progestational or an ti-proges ta tional under the experimental conditions described.