CHAPTEE XVIII. 



DEVELOPMENT OF THE GENITO-URINARY AND OF THE CIRCULA- 

 TORY SYSTEM. 



Development of the Wolffian bodies Ducts of the Wolffian bodies and ducts of 

 Miiller Development of the Wolffian ducts into the vasa deferentia, and 

 of the duets of Miiller into the Fallopian tubes Development of the testi- 

 cles and ovaries Development of the urinary apparatus External organs 

 of generation Malformations of the external generative organs Her- 

 maphEoditism Development of the circulatory system First, or vitelline 

 circulation Second, or placental circulation Branchial arches and devel- 

 opment of the arterial and the venous system Development of the heart 

 Description of the foetal circulation Third, or adult circulation. 



THE genital and the urinary organs are developed to- 

 gether, and are both preceded by the appearance of two large, 

 symmetrical structures, known as the Wolffian bodies, or the 

 bodies of Oken. These are sometimes called the false or the 

 primordial kidneys. They appear at about the thirtieth day, 

 develop very rapidly on either side of the spinal column, 

 and are so large as to almost fill the cavity of the abdomen. 

 Fig. 49, representing a specimen in the possession of Prof. 

 Dalton, shows how large these bodies are in the early life of 

 the embryon, at which time their function is undoubtedly 

 very important. 



Yery soon after the Wolffian bodies have made their ap- 

 pearance, we can distinguish, at their inner borders, two ovoid 

 bodies, which are finally developed into the testicles, for the 

 male, or the ovaries, for the female. At their external bor- 

 ders, are two ducts, on either side, one of which, the internal, 

 is called the duct of the Wolffian body. This finally disap- 

 pears, in the female, but is developed into the vas deferens, 



