The Variations in the Lipids of the Uterine Mucosa in the Pig.*

The structural changes in the uterine mucosa associated with the phenomena of estrus, menstruation, implantation of the embryo, pregnancy, and the puerperium have, for a long time, been of marked interest to the histologist. The staining reactions of the endometrium with Nile blue, Sudan III, Scharlach R, and osmic acid have indicated the possibility of a connection between the lipid content and the state of activity of the tissue. Most of the information we have on the subject is, however, based upon these staining reactions only, largely because of the technical difficulties involved in the study of such tissue by the chemical methods which have been available. The work of many investigators, beginning with Ancel and Bouin (1) has indicated that the pregestational prolification of the glandular tissue of the endometrium may be dependent upon the action of the hormone of the corpus luteum. Recently Corner and Allen (2) have prepared an active extract of corpus luteum and demonstrated a typical glandular proliferation of the endometrium following its injection into rabbits. This suggests that the cyclic changes in the chemical composition of the endometrium may be expected to run parallel to the various stages of growth and degeneration of the corpus luteum. It has seemed to us, therefore, that parallel chemical studies of the lipids of the