The Muellerian Ducts 19 



The Muellerian Ducts ; the Oviducts, Uterus and Vagina. 

 1. The Muellerian Ducts. 



Earl5' in embryonic life, before the genital ridges have become 

 well marked, about the second month in animals with extended 

 durations of pregnancy, the ducts of Mueller develop as two 

 ridges beneath the peritoneum near to, but outwardly from, the 

 WolfiBan ducts, from which they are said to arise as outgrowths, 

 and extend forwards from near the cloaca to or beyond the 

 WolfiBan glands. Appearing first as solid rods, they later become 

 excavated to constitute tubes, which end blindly at their posterior 

 extremity for a time but later open into the cloaca or common 

 vent of the digestive and urino-genital systems. As soon as 

 hollowed out, each vessel opens anteriorly into the peritoneal 

 cavit5' through a large funnel-shaped mouth, the future pavillion 

 of the oviduct of fimbriated end of the Fallopian tube. At this 

 time there are in this region, lying parallel and near to each 

 other, three separate ducts ; the ureter, the WolfiBan duct to 

 become the excretory duct of the male genital gland and the 

 Muellerian duct to become the genital tract of the female. The 

 posterior ends of the Muellerian ducts are in close contact at 

 first and later, at about the time of their opening into the cloaca, 

 they fuse together for a variable distance forward, their median 

 walls disappearing, resulting in the formation of a single tube as 

 far as the fusion extends. 



The Muellerian ducts later become differentiated into three 

 essentially separate segments through specialization of their 

 development, each having its distinctive function. The anterior 

 segment constitutes the oviduct or Fallopian tube with its 

 ampulla, or pavillion, which serves to receive the ovum from the 

 ovary and bear it, fetilized or unfecundated, into the wterine 

 cornu, or uterus ; the second or middle portion of the genital 

 tube constitutes the uterine cavity, in which the fetus may find 

 lodgement, attachment, nutrition and protection during its devel- 

 opment ; the third or posterior segment, the vagina, extending 

 from the uterus to the vulva, serves first as an essential copula- 

 tive organ and later as a passage for the fetus at the time of birth. 



The distance to which the fusion of the Muellerian duct ex- 

 tends forwards and the extent of the specialization of the different 



