The functions of the Corpus luteum. V.—Changes in the sterile horn during pregnancy, and their relation to changes in the Corpus luteum

Abstract

In confirmation of Courrier and Kehl (1930), Knaus (1930) and Hammond, it was found that the sterile horn of the rabbit undergoes characteristic pregestational changes lasting 12 to 14 days and afterwards regresses. The glands and epithelium disintegrate and blocks of debris are found in the lumen. From 14 days pregnant till parturition, the corpora lutea in all but one of the rabbits examined showed a disappearance of fats, blackening with osmic acid, from their inner region. The fat-containing zone decreased in size as pregnancy advanced and was reduced to a narrow rim at parturition. Since osmicated fats are found throughout sections of corpora lutea during the early days of pregnancy, their gradual disappearance and restriction in later stages probably indicates a decline in the elaboration of the luteal secretion. This may be correlated with the disintegration of the endometrium of the sterile horn. In the mouse, as in the rabbit, the changes in the sterile horn during the first half of pregnancy resemble those during pseudo-pregnancy, but during the second half, not regression, but an entirely new phase of development sets in. The uterine glands become greatly distended and their diameter may reach 250 [mu] to 300 [mu]. Regression, accompanied by some hemorrhage in the stromal tissue, begins just before parturition. This second phase of glandular development may be correlated with the enlargement of the corpus luteum at about mid-pregnancy (Deanesly, 1930). The possibility that the endometrium of the sterile horn is influenced by fetal or placental activity cannot be definitely excluded. No trace of such uterine change was found in the sterile horn of the pregnant rat. In the guinea-pig the morphological changes in the sterile horn during pregnancy are as slight as during pseudo-pregnancy, and consequently give no clue to the duration of luteal influence. Histological study of the corpora lutea after Flemming fixation suggests that the majority of them remain functional throughout pregnancy ; osmicated fat increases up to and after parturition.