THE FEMALE REPRODUCTIVE ORGANS 



2 43 



this tube lies parallel and in close proximity with the Wolffian duct, its 

 cephalic end opening into the body-cavity, while its lower extremity 

 terminates at first within the cloaca and later within the uro-genital 

 sinus. It is necessary further to distinguish three groups of the 

 Wolffian tubules, since the fate of these portions of the foetal organ 

 varies ; these divisions are the anterior group, constituting the pro- 

 nephros, the middle or sexual segment, and the posterior rudi- 

 mentary tubules, which give rise to atrophic structures. 



The development of the sexual glands includes a primary 

 indifferent and a later specialized stage. 

 During the period when the Wolffian body FIG. 280. 



has attained its greatest growth there ap- 

 pears on the ventro-mesial surface of the 

 organ a localized thickening of the meso- 

 thelial elements. This proliferation pro- 

 duces an eminence, the earliest trace of the 



Sexual gland. This for SOme time is in- Section of peripheral zone of in- 



different, since its appearance is identical diff ; rent sexual gl * n , d [ ron ! rabblt 



* * embryo : e t mesothehal cells con- 



in the tWO SeXeS. The indifferent SeX- stituting the later germinal epithe- 



ual glands soon exhibit two kinds of * ium ; *',?; sma11 el " ments . d ' rived 



from proliferation of mesoi hdium ; 



elements, the loosely-packed proliferated o, large primordial sexual ceils. 

 small mesothelial elements and the 

 sparingly-distributed much larger primordial sexual cells. 



In the male, the further changes within the sexual gland include 

 extended proliferation of the early mesothelial elements and their 

 grouping as epithelioid cylindrical masses, the sexual cords ; within 

 the latter lie the large primordial sexual cells, their number, however, 

 in the developing testicle being distinctly smaller than in the corre- 

 sponding female organ. The sexual cords become the seminiferous 

 tubules, remaining solid cylinders throughout fcetal life. The par- 

 ticular fate of the large sexual cells is still uncertain. The surround- 

 ing mesodermic tissue grows into the mesothelial mass and contributes 

 the intertubular connective tissue as well as the denser portions of the 

 framework represented by the tunica albuginea and the trabeculae. 



The system of canals forming the connection between the testicle 

 and the epididymis, including the vasa efferentia and the coni 

 vasculosi, are derived from the tubules of the Wolffian body ; 

 by the ingrowth of these canals into the embryonal testicle the isolated 

 sexual gland is provided with excretory passages. Other remains 

 of the lower tubules of the Wolffian body constitute the para- 

 didymis. The main tube of the epididymis and the vas deferens 

 are the direct representatives of the Wolffian duct. 



The Miillerian duct in the male is atrophic, since its extreme 

 anterior and posterior parts alone persist ; these remain as the non- 



