THE DEVELOPMENT OF THE UROGENITAL SYSTEM. 437 



found in the testicle. For a further discussion of these see chapter on Terato- 

 genesis (XIX). 



The Ovaries. — Congenital absence of both ovaries is rare; defective 

 development of one is more common. Either anomaly may occur with or 

 without defects in the other genital organs. Occasionally the ovaries remain 

 rudimentary, their function as egg-producing, organs never being assumed. 

 Malpositions, due to partial or complete failure in the normal descent into 

 the pelvis (p. 426), are not infrequent. Sometimes, on the other hand, they 

 descend to the inguinal canal and may even pass through the latter into the 

 labia majora. 



Ovarian cysts occur frequently. Some of these (follicular cysts) may arise 

 during postnatal life as dilatations of Graafian follicles.- Others probably 

 arise during foetal life in the same manner. Certain other forms of ovarian 

 tumors, known as cystadenomata, are possibly to be considered as derivatives 

 of the epithelium of the medullary cords which in normal cases disappear 

 entirely (p. 410; also Fig. 366). A discussion of the origin of teratoid tumors of 

 the ovary will be found in the chapter on Teratogenesis (XIX). 



The Oviducts, Uterus and Vagina. — Absence of the oviducts is usually 

 associated with malformations of other parts of the genital tract. On the other 

 hand, normal oviducts may be present in conjunction with defective uterus 

 and vagina. Atresia may occur at the uterine or fimbriated end, or at any 

 intermediate point. 



The majority of the malformations of the uterus and vagina can be at- 

 tributed to defective processes of development in the caudal ends of the Miiller- 

 ian ducts. It will be remembered that the caudal ends of these ducts normally 

 fuse to form a single medial tube which opens into the urogenital sinus, and 

 which constitutes the anlage of the uterus and vagina (p. 419; Fig. 363). It is 

 obvious that any defect in this fusion will result in some degree of duplicity 

 in the two organs in question. The fusion may be almost complete, the result- 

 ing abnormality being merely a small pocket which forms, at each side of the 

 fundus, a continuation of the cavity of the uterus. There may be a greater 

 degree of imperfection in the fusion, resulting in a partial division of the uterus 

 into two horns — bicornuate uterus. The wall between the two Mullerian ducts 

 may remain patent in the entire uterine portion of the tract, thus giving rise 

 to a bipartite uterus. If the wall between the ducts remains intact throughout 

 both uterine and vaginal portions, the result is a complete division of the utero- 

 vaginal tract — uterus didelphys. Occasionally the uterine portion of one 

 Mullerian duct may fail to develop properly and becomes a solid cord, resulting 

 in an unicornuate uterus. 



Not infrequently the uterus remains rudimentary — infantile uterus. This 

 anomaly is usually accompanied by stenosis of the vagina. Stenosis or other 



