The endocrine factors responsible for the maintenance of pregnancy: studies in the interruption and prolongation of pregnancy in the rat and the mouse

Experiments have been performed which examine some of the effects upon the pregnant animal of injections of an extract of human pregnancy urine, and of an alkaline extract of anterior pituitary, also of the implantation of anterior pituitary tissue. Pregnancy was interrupted in some cases, and in others prolonged.Additional data were collected regarding the effects of a corpus luteum extract upon foetal development, and of partial and entire removal of the ovaries during pregnancy. The extract was without appreciable effect up to the 15th day of Pregnancy. It was confirmed that ovarian secretion is essential to pregnancy, and that its partial removal in the yearly stages may cause pregnancy to be interrupted. A study was made of the grówth of the mother and foetus during pregnancy, haemorrhage, and the cell content of the vagina under the influence of the various treatments administered.Factors concerned in the interruption and prolongation of pregnancy have been examined. It is highly improbable that an interruption of pregnancy is due to an "oestrogenic effect". In the animals in which pregnancy was interrupted, the ovaries were found to be full of corpora lutea; the possibilities of an interference with an extra- ovarian factor concerne in the pregnancy mechanism are discubsed The prolongation of pregnancy appears to be due to a continuation of the activity of the corpus luteum and to an inhibition thereby placed upon factors responsible for parturition.Evidence in favour of the existence of Rho factors (pituitary) is examined, and.it is concluded that the data, so far obtained, do not warrant making the conclusion that there are either one or two factors