Abstract

A histological study of the action of estrin administration during the course of pregnancy indicates:

1. That in pre-implantation stages, the uterus, when exposed to an adequate dose of estrin has a hyperplastic mucous membrane, considerably fibrosed, and the secretion in its lumen has practically no coagulable material in it, resembling rather the secretion which dilates the uterus at estrus.

2. That pregnancy in post-implantation stages is terminated by killing the embryo, without necessarily involving any morphologic changes except the absence of the characteristic edema of pregnancy.