. Gynecology : . uction remaining until thefourth or fifth month, when the uterus and vagina acquire a single communi-cating lumen, which shows no signs of the former double formation, except aslight depression at the fundus where the partition ended. It is important tokeep clearly in mind this particular part of the embryology of the genital tractin order to comprehend the various types of maldevelopment of the uterus. At about the beginning of the fifth month the uterus becomes differentiatedfrom the vagina by the formation of the vaginal portion (cervix). At the end 436 DEFECTS OF DEVELOPME
. Gynecology : . uction remaining until thefourth or fifth month, when the uterus and vagina acquire a single communi-cating lumen, which shows no signs of the former double formation, except aslight depression at the fundus where the partition ended. It is important tokeep clearly in mind this particular part of the embryology of the genital tractin order to comprehend the various types of maldevelopment of the uterus. At about the beginning of the fifth month the uterus becomes differentiatedfrom the vagina by the formation of the vaginal portion (cervix). At the end 436 DEFECTS OF DEVELOPMENT 437 of the fifth month the fundus of the uterus rounds out, so that all appearance ofthe former double character of the uterine body disappears. The wall of theuterus acquires muscle-fibers at about the fifth month, at which time also thehymen appears as a special differentiation of the lower vaginal segment. Atbirth the uterine body is small, thin walled, and insignificant in comparisonwith the cervix. 3>o. Qpevuncs_] NivJ^.C- Fig. 167.—Diagram Showing the Relationship op the Mullerian and Wolffian Ducts andtheir Openings into the Urogenital Sinus. Even in the earliest periods can be noted a difference in the character of theepithelium in different segments of the Mullerian ducts. The upper portionsfrom which the tubes and uterus are formed first become hollow, and are linedwith a simple cylinder epithelium, while the vaginal part, as was stated above,remains until a later period a solid structure, filled with large cuboidal epithelialcells. The layer of epithelium which lines the upper parts does not becomeciliated until extra-uterine life. The mucous membrane of the uterine body is in the embryo very little 438 GYNECOLOGY differentiated from that of the cervix, while the branching folds, which charac-terize the cervix in the adult (arbor vitse), are, in the embryo and child, con-tinued to the fundus of the uterus (Fig. 168). The establishment of secretingglan
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