Observations on the “reversed” uterine horn of the rabbit.

It is universally believed that the ciliated epithelium of the oviducts and uterus of mammals play the chief role in the transport of the ovum from ovary to uterine cavity. A few authors, however, seem to regard the contractions of the uterine muscle as being more important

The above belief is based on two facts, (1) the direction of the ciliary movement being vaginal-ward and (2) the appearance of small particles in the uterus or vagina, after being introduced into the general peritoneal cavity.

In attempting to establish the corollary, namely that if the direction of the cilia be reversed, the ovum could not progress beyond the part reversed, we have found that the reversal of the uterus offers no impediment to the passage of the ovum.

The method employed was to divide the uterine horn (of rabbits) on each side, in two places 2.5 to 3.0 cm. apart and to reunite the cut ends after reversing each segment. The animals were then allowed to heal (a laparotomy being performed in some cases to determine the condition of the anastomosis) and were later mated.

Six animals thus experimented upon have all become pregnant. Three of the animals were subjected to observation before term, the remainder were left to complete their pregnancy.

It was found that implantation occurred most frequently within the reversed segment and in one instance in the portion of the uterus between the segment and the cervex uteri. It is thus established, that an ovum may travel across two anastomoses apparently against an opposing ciliary movement.