A study of the distribution of dead and resorbing embryos in the rat uterus

Abstract

"The characteristic method of elimination of a dead embryo from the uterus of a polytocous animal is by resorption. This involves an enzymatic digestion of the dead embryo la situ, the products of digestion being eliminated from the uterus by the maternal circulatory system. In contrast to abortion which is the usual consequence of embryonic death in most monotocous species, resorption of an embryo makes possible the continuation of development of any living embryos remaining in the uterus (Long and Parks, 1924). It has been observed that when partial litter mortality occurs, the dead embryos may be found in various states of resorption, indicating that embryos may die at different stages of gestation in the same uterus (Hollander and Strong, 1950; Fortuyn, 1920; and Gillman, Gilbert, and Gillman, 1948). The degree of resorption can be used as an indication of the relative time of death of the embryo. Although never the primary subject of investigation, the distribution of dead and resorbing embryos in the uterus has been thought by some workers to be related to the area of the uterus in which the embryos are implanted (Edwards and Fowler, 1959). Unpublished preliminary experiments done in the Zoology Department at the University of Missouri using parous albino rats suggested that there was a tendency for the embryos implanted in the cervical and ovarian ends of the uterine horn to die and be resorbed earlier than the embryos implanted in the central part of the uterine horn. The present investigation has been directed toward finding whether or not embryonic death and subsequent resorption occurs more frequently in certain areas of the uterus of nulliparous albino rats."--Introduction.