Diffusivity Summary of

Various human urinary gonadotrophins and pregnant mares ' serum (PMS) frequently gave log dose-log response lines of divergent slope in the assay of Claringbold & Lamond [1957]. This is contrary to their findings and shows dissimilarity in the early action ofdifferent gonadotrophins. There were marked differences in the response of mice from different colonies to PMS and human chorionic gonadotrophin (HCG). Results by the method of Claringbold & Lamond contrasted more sharply with those of an 'HCG-augmentation ' assay for follicle-stimulating hormone than did results of a 72 hr assay using uterine response. It has been claimed [Emmens, Claringbold & Lamond, 1957; Claringbold & Lamond, 1957; Lamond & Claringbold, 1958] that the early effect of various gonadotrophins on the mouse uterus is always the same whether they are pregnant mares ' serum(PMS) or human chorionic gonadotrophins (HCG). This implies either that these gonadotrophins are qualitatively similar or that the assay which depends on this response may be specific for a certain aspect of the activity of dissimilar gonado¬ trophins. The subject has been investigated by comparing assays depending upon this early response [Claringbold & Lamond, 1957] with others depending upon th