=The Vagina.=—The vagina is a hollow organ, about four inches long, attached to the cervix above and the vulva below. It is an elastic sheath bounded in front by the bladder and behind by the rectum. Under normal conditions, this tube easily admits one or two fingers, but during labor it dilates enormously to allow the head to pass. The vagina is lined with a thick mucous membrane, ridged and roughened by folds, which are called rugæ. Thus a continuous channel connects the ovary with the outside and through it pass, at appropriate times, the ovule, the menstrual blood, the uterine secretions, the child, the placenta, and the lochia. =The Uterus.=—The uterus (womb) is a pear-shaped organ, flattened from before backward, and composed of unstriped or involuntary muscle cells and connective tissue. Normally the virgin uterus measures from two and one-half to three inches in length, and weighs about two ounces. It is suspended in the middle of the pelvis by strong ligaments, so that the fundus inclines gently forward against the bladder. When the bladder fills, the uterus is pushed backward. Most of the organ is internal, but a small part of the lower pole is grasped by the vagina, in which the lower end with its invaluable aperture, the os, dips and swings. The part above the vagina is called the body or fundus, and is covered with the serous membrane (peritoneum) that lines the abdominal cavity. Below the fundus is the cervix or neck, which lies partly above and partly within the vagina. The cavity of the uterus is usually closed by the apposition of the walls. The inner surface is covered with a peculiar kind of membrane called the endometrium, which is highly vascular. The uterine cavity opens into the vagina through the os, which is small and round in the nulliparous woman, and slit-shaped or gaping in the woman who has borne a child. [Illustration: Fig. 4.—Uterus and appendages. On either side of the uterus will be seen the ovary, the fimbriated extremity of the tube, the tube, and the round ligament. The vagina lies open below. (Lenoir and Tarnier.)] =Fallopian Tubes.=—On either side of the upper end of the uterus are the orifices of the Fallopian tubes, through which the egg, escaping from the ovary, finds access to the uterine cavity. These tubes extend outward from the uterus about four inches, and terminate in a bell-shaped opening with long, ragged fingers which hang loosely down toward the ovary. The tubes are lined by epithelial cells having hair-like projections, (ciliæ) which wave automatically toward the uterus. Thus impelled by a gentle current, the egg moves definitely along the tube toward the uterus and against this current the spermatozoa force their way to meet and fertilize the egg.