Polyps in the Guinea Pig*

Under the term endometrial polyps is grouped a variety of tumors of polypoid structure which are attached to the inner uterine wall by pedicles of variable length and thickness. Although their histologic characteristics differ greatly, the most common variety has a tissue structure similar to that of the surrounding endometrium. The polyps may be single or multiple; small, or large enough to occlude the uterine lumen. In the human, sloughing of the tip in the pedunculated variety may be the cause of persistent hemorrhage (1, 92). Endometrial polyps in laboratory and domestic animals occur rarely and apparently have not been produced experimentally in any animal. During an investigation on the embryo-endo metrial interrelationship at the time of implanta tion in the guinea pig (3), it was found that endo metrial polyps could be produced if small inert objects were implanted just below the epithelium of the endometrium at any time between the second and seventh days after ovulation. There fore, an investigation was undertaken to deter mine : (1) the frequency of occurrence of endo metrial polyps in the normal guinea pig; (92) the time during the reproductive cycle that polyps could be produced by the techniques to be de scribed; (3) whether polyps could be induced to develop in all regions of the endometrium; and, (4) the ultimate fate of the polyps.