The Effect of Estrogenic Hormones on the Bacterial Content of the Uterus *

The impression is general that the uterus under normal conditions does not harbor bacteria. This is supposedly true of both man and laboratory animals. Following parturition, however, serious uterine infections may occur. In laboratory animals short periods of treatment with estrogenic hormones have usually provided very little evidence of uterine infection.' Extensive leukocytic infiltration, presumably aseptic, has appeared after the action of estrogenic hormones has ceased. This regressive phase was quite similar to the post-ovulatory stage, late metestrum, in the normal animal. WAThen rats6' 8, 11 or mice2' 4, ' were treated with estrogens for long periods of time in attempts to produce mammary and cervical cancers, inflammatory or suppurative uterine lesions or pyometra appeared. In some animals these lesions were extreme; the horns of the uteri were distended with pus, sometimes the gut was constricted by adhesions, and at times a generalized peritonitis occurred. If uteri were transplanted in a subcutaneous position or ligated from the cervical canal, pyometra did not occur.9 In order to test further the possibility that treatment with estrogenic hormones might induce a condition favoring infection, the following series of experiments were undertaken.