Mechanism controlling entry of ova into rabbit uterus

A mechanism is present at the lower end of the rabbit oviduct which prevents the entry of ova into the uterus until the reproductive organs come under the influence of progesterone. In normal rabbits, distention of the oviduct caused by ligating the infundibular end, recedes between the 60th and 72nd hour post coitum. Estrogen injections prolong distention. Progesterone does not markedly speed up ovum transport and is effective only when it can overcome the effect of endogenous estrogen. Circular muscle activity was recorded at three levels of the oviduct. Activity in the ovarian end greatly exceeded that in the lower sections of the tube. At the uterine end activity was very slight or not present at all. Several attempts to demonstrate the presence of edema in the tubo-uterine junction were unsuccessful.