Internal Migration of Ova in the Cat. ∗

Abstract

During other investigations, we have had occasion to interrupt one uterine tube to study the changes which might occur during pregnancy in the occupied and unoccupied horns. This report deals with observations on the uterine horns of 7 cats in which the right uterine tube was interrupted in each case a number of weeks before the animal was bred.

In 3 animals, the operative procedure consisted merely of ligation (with silk thread) of the right uterine tube in 2 places and section between the ligatures. These animals were bred and were sacrificed in the 7th week of pregnancy. Fetuses were found in both horns in all 3 animals. We were unable to find any macroscopic evidence of regeneration of the uterine tubes and in 2 animals the silk ligatures were found encircling the cut ends. Further evidence of migration of the ova from the unoperated to the operated side was obtained by a study of serial sections of both fragments of the tube and the tubal end of the uterine horn from the operated side of one of the animals. No histological evidence of a reestablishment of the lumen was present.

In order to test further the possibility of migration from one horn to the other, we transected the uterine tubes in a second series of cats. Here we sectioned the uterine tube midway between its 2 ends, cauterized the free end of the ovarian half and buried the free end of the uterine half in the muscle of the uterine horn. When these animals were sacrificed at different intervals during their pregnancies, there were fetuses in both horns of 3 of the 4 cats. In all of them, what had been the free end of the uterine half of the tube was still buried in the uterine musculature and the silk thread used to sew the tube into the uterine muscle was still in place.

In this series of 7 cats in which the right uterine tube had been sectioned, there were 21 fetuses with a distribution of 10 in the right horns and 11 in the left ones. The average litter was 3. In another series of 13 animals which had been subjected to another abdominal operation, there was an average litter of 4.7. This indicates that there was a reduction in the average number of fetuses in the litters following section of the right uterine tube. It also demonstrates a fairly equal distribution of fetuses in the 2 uterine horns.