Congenital malformations are found in all parts of the genital tract. Some of the more common forms, like arrested development of the uterus, have been referred to in the previous pages. Others will briefly be considered here. Reference to the method of development of the sexual organs will elucidate this subject. The Fallopian tubes, the uterus, and the vagina are developed from two embryonic structures called the ducts of Müller. These ducts become fused, first at the lower extremity, between the sixth and eighth weeks of fetal life (Fig. 175). The early genital tract thus formed is consequently divided throughout by a septum, which normally disappears during fetal development, so that there results one vaginal and uterine tract, from which the Fallopian tubes branch. [Illustration: FIG. 175.--Diagrams showing the development of the vagina and the uterus from Müller’s ducts.] The most important malformations of the vagina and the uterus arise from arrest, at any stage, of this normal developmental process. Very rarely the uterus is completely absent, or it may be represented by a small band of muscular and connective tissue stretched across the pelvis. In other cases the cervix is well formed, while the body of the uterus is but poorly developed. We have seen that this condition is often associated with pathological anteflexion of the uterus. =Uterus Unicornis.=--Sometimes there is arrest in the development of one of Müller’s ducts, so that the uterus becomes one-sided or one-horned and presents only one formed Fallopian tube. In such a case both ovaries may be present. =Uterus Didelphys.=--Müller’s ducts may unite only as far as the top of the vagina, no fusion whatever taking place in the uterine portion. In such a case two separated uterine bodies are produced; the condition of double uterus exists (Fig. 176). [Illustration: FIG. 176.--Uterus didelphys and double vagina.] =Uterus Bicornis Duplex.=--In this variety of malformation development has proceeded a step farther than in the preceding variety. The uterine bodies have become externally united. There is, however, no fusion of the cavities. Two cavities are present, opening into a double vagina. =Uterus Bicornis Unicollis.=--Here the development of the cervix and the lower part of the uterus is normal. The upper parts of the body of the uterus have not become fused, and diverge sharply from each other. The organ is two-horned (Fig. 177). [Illustration: FIG. 177.--Uterus bicornis unicollis (Winckel).] =Uterus Cordiformis.=--In this variety the two halves of the uterus are united throughout. Externally on the fundus there appears a slight depression, which, with the broad body of the uterus, demonstrates the imperfection of development. The name is derived from the resemblance to the conventional heart-shape.