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In order to clarify the central effect of oestriol quantitatively 5 day old male and female rats were treated with one subcutaneous injection of oestriol or 17β-oestradiol. From the 60th day of life these animals were mated with proven fertile partners. The animals were considered sterile if no pregnancy occurred within 60 days of the observation period. With reference to the standard 17β-oestradiol an activity was found for oestriol of 0.125 when tested on male rats and an activity of 0.26 when tested on female rats. Male animals treated with 17β-oestradiol were twice as sensitive as female rats. In female and male rats oestriol caused an identical central stimulation.The central effect of oestriol in relation to the standard 17β-oestradiol was found to be much lower than former investigation had shown. Hence this effect especially with only one injection must be due to the more rapid elimination of oestriol as compared with the standard 17β-oestradiol.

The musculature of the Fallopian tube is hyperactive during the time of ovulation, but the mechanism which activates the tube is obscure. A humoral regulation of tubai motility is more probable than a nervous one, although it is not known to what extent biogenic compounds (tissue hormones) can stimulate the tubes.We have investigated this question on a quantitative pharmacological basis using eighty-four human tubes on the day of removal. Strips were cut from the infundibular end and suspended in 10 ml Krebs-Henseleit solution at 32° C and aerated with carbogen. The contractions of the preparations were recorded isotonically on smoked paper. The experiments were designed to yield dose-response curves from which the EC50-values and other parameters mentioned in Table 1 were determined. Text-fig. 1 gives two typical examples of dose-dependent responses and shows not only that tubai strips in vitroproduce powerful contractions, but also that there are great quantitative differences between the endecapeptide eledoisin, and acetylcholine. Noradrenaline and the peptides oxytocin, bradykinin, kallidin, and angiotensin were practically inactive. The active substances are summarized in Table 1. In contrast with the well-known biogenic amines acetylcholine, histamine, and