MORPHOLOGY OF THE HUMAN URINOGENITAL TRACT. 369 



' In regard to the relining of the vagina from the Wolffian 

 bulbs, I wish to point out that in the ureter and bladder we 

 have a niucuous membrane made up of a many-layered epi- 

 thelium. The interesting query suggests itself as to the origin of 

 this lining. The ureter splits off from the Wolffian duct and is 

 thus epiblastic. The bladder, however, is allantoic at its apex, 

 derived in the main from the primitive gut {vide postea, p. 381), 

 and is thus hypoblastic in origin. Is it relined through the 

 epiblastic ureter as the vagina is through the Wolffian duct ? It 

 would be interesting to know what naked-eye changes took place 

 in that mucous membrane of extroverted bladder after the ureters 

 had been transplanted with the rectum. Probably the exposed 

 bladder would become skindike and lose its moist condition. 



IX. Summary. 



1. The genital organs in the adult mammal arise from, and 

 in connection with, the Wolffian bodies, the Wolffian duct and 

 the ducts of Milller. 



2. In the lowest female mammal examined (rat kangaroo 

 as type of Marsupials) the urinogenital ducts are least modified ; 

 the Wolffian ducts hchuj represented hy the lateral vaginal canals 

 and ep6ophorun,ioh'ile tlie paroophoron, is 2iresent as a duct in the 

 centre of the ovary. The Miillerian ducts are present as the 

 Fallopian tubes and uterine cornua, while the central vaginal 

 canal represents the rest of the Miillerian tract. The urino- 

 genital sinus is present apparently unaltered, and the whole 

 arrangement is like the human fatal condition at the sixth to 

 the seventh week. 



3. In the adult human female the genital tract has the 

 Wolffian body represented by the epoophoron (normally 

 present) and by traces of the paroophoron at the hilum of the 

 ovary. The Wolffian duct is represented normally near the 

 epoophoron and rarely by occasional traces in the broad liga- 

 ment and uterus. The lowest segment of the vaginal portion 

 of the Wolffian duct forms the hymen by the coalescence of 

 bulbous proliferations there, and cells from these replace the 

 primitive lining of the Miillerian vagina. 



The vagina is Miillerian only in its upper two-thirds ; the 



