THE UEO-GENITAL SYSTEM. 



113 



minal wall and form the round ligament of the uterus. The 

 point from which the ingrowth springs becomes the internal 

 abdominal ring. Others grow out into the labium majus, carry- 

 ing with them a process of peritoneum — the canal of Nuck. The 

 inguinal canal and external abdominal ring and extra-abdominal 

 part of the round ligament are thus formed. 



Formation of Uterus and Vagina. — Within the genital cord 

 the Mullerian ducts fuse and form the uterus and vagina (Fig. 87). 

 In all the members of the vertebrate series below and including 



rd. lig. 

 uterus 

 Muller. duct 

 cloaca. 



pen. of. red. ff 



rFallop. 

 X tube 



fallop. 

 tube 



,-sa round lig. 

 uterus 



I- —uag. 



Fia. SS.— Evolution of the Human Form of Uterua. 

 A Form seen in lowest mammals, reptiles, amphibians, fishes, and in the 2nd 

 month human foetus. B. Form of Mullerian Ducts in rodents. C. Form in 

 Camivora, etc., and in the 4th month human foetus. D. Form found in man 

 and higher primates. 



the Monotremes, the Mullerian ducts remain separate and open 

 in the cloaca (Fig. 88 A). The process of fusion begins in the 

 3rd month. The septum formed by the fused mesial walls 

 (Fig. 89) disappears first in the region of the uterine cervix ; the 



H 



