DEVELOPMENT OF URINARY AND GENERATIVE ORGANS 1423 



erulus. These tubules increase in number, and collectively constitute the mesonephros or 

 Wolffian body (Figs. 1178, 1179). At the beginning of the second month this body forms an 

 elongated spindle-shaped structure, which projects into the ccelomic cavity at the side of the dorsal 

 mesentery, and reaches from the septum transversum cephalad to the fifth lumbar somite caudad. 

 The Wolffian body persists and forms the permanent kidney in fishes and amphibians, but in 



( Stroma 



Genital J of ovary, 

 ridge. \ Primitive _'| 

 [ ova. 



Mesentery.- - 



Wolffian duct. 



^.Mullerian duct. 



'---Wolffian 

 -"" tubules. 



-Body wall. 





 FIG. 1178. Section of the urogenital area of a chick embryo of the fourth day. (Waldeyer.) 



reptiles, birds, and mammals it is superseded by the metanephros, which forms the permanent 

 kidney in these animals. The anterior tubules of the Wolffian body become attached to the 

 sexual eminence or genital ridge, from which the ovary in the female and the testicle in the male 

 are developed. During the development of the permanent kidneys the Wolffian bodies atrophy, 

 and this process proceeds to a much greater extent in the female than in the male. 



Millie rian ducts. 



FIG. 1179. Enlarged view from the front of the 

 left Wolffian body before the establishment of the 

 distinction of sex. a, a, 6, d. Tubular structure of 

 the Wolffian body. e. Wolffian duct. /. Its upper 

 extremity, g. Its termination in x, the urogenital 

 sinus, h. The duct of Mtiller. i. Its upper, funnel- 

 shaped extremity, k. Its lower end, terminating in 

 the urogenital sinus. /. The mass of blastema for 

 the reproductive organ, ovary, or testicle. (From 

 Farre, after Kobelt.) 



FIG. 1180. Urogenital sinus of female 

 human embryo of eight and a half to nine 

 weeks old. 



In the male the Wolffian duct persists, and forms the tube of the epididymis, the vas deferens, 

 and common ejaculatory duct, while the seminal vesicle arises as a lateral diverticulum from its 

 caudal end. The cephalic Wolffian tubules form the rete testis, vasa efferentia, and coni vas- 

 culosi of the testis; while the caudal tubules atrophy or are represented by the occasional vasa 

 aberrantia of the globus minor and by the paradidymis. 



In the female, the Wolffian bodies and ducts atrophy. The remains of the Wolffian tubules 

 are represented by the epoophoron and the paroiiphoron (p. 1409), while the cephalic portion of 

 the Wolffian duct sometimes persists as the fiineu'onless duct of Gartner (-Fig. 1104). 



