THE ORGANS OF THE MIDDLE GERM-LAYER. 



393 



(B) The Metamorphosis in the Female. Descensus ovariorum. 



The metamorphosis of the primitive embryonic fundaments in the 

 female is in many particulars the opposite of that in the male, inas- 

 much as parts which are made use of in the latter become rudi- 

 mentary in the 

 former, and 

 vice versa (com- 

 pare with one 

 another the 

 diagra ms 

 .shown in figs. 

 219, 222, and 

 225). Whereas 

 in man the 



mesonephric 

 duct becomes 

 the vas defer- 

 ns, in woman 



tJic Miilkrian 



hbt' 



duct (fig. 225 

 t, ut, sch) as- 

 sumes the func- 

 tion of conduct- 

 ing away the 

 ova, while the 

 mesonephric 

 duct (ug) and 

 the primitive 

 kidney (ep, pa) 

 become rudi- 

 mentary. 



The prone- 

 phric duct in 



advanced human embryos of the female sex is still demonstrable as 

 an inconspicuous structure in the broad ligament and at the side 

 of the uterus ; in the adult it has, as a rule, entirely disappeared, 

 except the terminal portion, which is enclosed in the substance of 

 the neck of the uterus, where it is distinguishable, but only by 

 means of cress sections, as an extraordinarily narrow tubule (BEIGEL, 

 H. DOHRN). In many Mammals, as in Ruminants and Swine, the 



Fig. 225. Diagram to illustrate the development of the female sexual 

 organs of a Mammal from the indifferent fundament of the uro- 

 genital system, which is diagrammatically represented in fig. 219. 



The persistent parts of the original fundament are indicated by con- 

 tinuous lines, the parts which undergo degeneration by dotted 

 lines. Dotted lines are also employed to show the position which 

 the female sexual organs take after the completion of the descensus. 



n, Kidney ; ei, ovary ; ep, epoophoron ; pa, paroophoron ; hy, hydatid ; 

 t, Fallopian tube (oviduct) ; ug, mesonephric duct ; ut, uterus ; sch, 

 vagina ; hi, ureter ; hbl, urinary bladder; kbl', its upper tip, which 

 is continuous with the ligamentum vesico-umbilicale medium ; hr, 

 urethra ; vv, vestibulum vaginae ; rm, round ligament (inguinal 

 ligament of the primitive kidney) ; lo', ligamentum ovarii. 



The letters t', ep', ei', lo' indicate the positions of the organs after the 

 descent. 



