The observations here described arose out of research (now in the press) made by Florey and myself for the Birth ontrol Investigation Committee. Wishing to ascertain whether aspiration was exerted by the uterus during coitus, we injected animals per vaginam with suspensions of carmine or grraphite immediately before copulation. When examining sections of the vaginæ later, I was struck by the apparent inclusion of particles of the injection mass in the vaginal epithelial cells. Subsequent study has demonstrated that the epithelium of the upper segment of the rabbit's vagina is definitely phagocytic, as the experimental evidence detailed below will show. II. Material and methods . The present study is largely based upon a series of 40 rabbits. Two methods of experimental approach were used.