FIG. 11.—Diagrams of sections of virgin and multiparous uteri. ] The uterus is covered, front and back, by a fold of the _peritoneum_, except the lower part of the anterior wall where the peritoneum is reflected up over the bladder. It is lined with a thick, velvety, highly vascular mucous membrane, the _endometrium_, the surface of which is covered by ciliated, columnar epithelium. Embedded in the endometrium are numerous mucous glands which dip down into the underlying, muscular wall. The uterus as a whole is comprised of three parts: the _fundus_, that firm, rounded, head-like part above; the _body_, or middle portion, and the _cervix_, or neck, below. It is in the body and cervix that we find the long, narrow uterine cavity, divided by a constriction into two parts. The cavity of the body is little more than a vertical slit, being so flattened from before backward that the anterior and posterior surfaces are nearly if not quite in apposition. It is somewhat triangular in shape with an opening at each angle. (Fig. 11.) The lower of these openings leads into the cavity of the cervix through a constriction termed the _internal os_, while at the _cornua_, or two upper angles, are the openings into the Fallopian tubes. The cavity of the cervix is spindle-shaped, being expanded between its two constricted openings, the internal os above and the _external os_ below, which opens into the _vagina_. The external os in the virgin is a small round hole but has a ragged outline in women who have borne children. This oblong, muscular body, the uterus, is suspended obliquely in the centre of the pelvic cavity by means of ligaments. In its normal position the entire organ is slightly curved forward, or ante-flexed, the fundus being directed upward and forward and the cervix pointing down and back. This position is affected by a distended bladder or rectum, and also by postural changes in the body as a whole. The _cervix_ protrudes into the anterior wall of the vagina for about one-half inch and almost at right angles, since the vagina slopes down and forward to the outlet. The upper part of the uterus is held in position by means of ligaments, the lower part being embedded in fat and connective tissue between the bladder and rectum. This more or less of a floating position makes possible the enormous increase in size and upward push or extension of the uterus during pregnancy. The pregnant uterus becomes soft and elastic as it grows. At term it is about a foot long, eight to ten inches wide, and reaches up into the epigastric region. This growth is due in part to the development of new muscle fibres and in part to a growth of the fibres already existing in the uterine wall. After labor the uterus returns almost, but never entirely, to its former size, shape and general condition.