Uterine Grafts

Foetal tissues were transplanted into the pseudo-pregnant uterus of the rabbit, a suitable position for such grafts owing to the raised nutrition of the uterus occurring in the early stages of pseudo-pregnancy. Several tissues particularly large amounts of cartilage and small quantities of epithelial tissue persisted and grew, the former undergoing ossification. The growth of these foetal tissues in the pseudo-pregnant uterus did not cause the corpus luteum of pseudo-pregnancy to persist or the mammary gland to thicken as in pregnancy. Since—(a) the foetal tissues only grew where they were attached to the muscle layer of the uterus, although every effort was made to attach them to the mucosa; (b) the parts of the grafts lying in connection with the mucosa were absorbed rather than nourished; and (c) the introduction of living foetal tissue failed to cause any further development of the deciduomata which were produced by cutting the pseudo-pregnant mucosa—it is suggested that normally the attachment of the foetus is caused by the active erosive (digestive) agency of the foetal trophoblast, a function which is absent in the cells of the foetus itself. It seems probable that just as the small deciduomata are formed as a response to a cut so the large maternal placenta is formed as a response to the continuous erosion by the foetal trophoblast.