DEVELOPMENT OF GENERATIVE OHGANS. 



757 



589 



passages are all closed up, and the allantoic vessels obliterated at 

 the navel, after piilmonic respiration is established at birth. 



411. Definition of Male and Female Organs. In the Mam- 

 malian as in other vertebrate embryos the urogenital parts, before 

 showing distinction of sex, appear in a seemingly more complex 

 or multiplex condition than when per- 

 fected at a later stage-. As in fig. 589, 

 we recognise the basis of the true or 

 persistent kidneys, , with their duct, 

 e\ the antecedent deciduous kidney. 



/ " 



or 'Wblffian 5 body, Z>, is here on the 

 wane, with its excretory duct, f\ the 

 beginning of the essential genital 

 gland is marked c, the adrenals, d, 

 and the tubes called ' ducts of Mill- 



Urogenital parts of Embryo. LXXIV. 



ler,' cj. 



In the male Mammalian embryo the 

 duct,^, becomes connected by a white 

 granular process with a similar one 



from the gland, c, on the inner side of 



~ 



the Wolffian body : by the union of 

 these offshoots is formed the epididy- 

 mis, and the gland c can then be de- 

 termined as the testis : the ducts, 

 y, shrink and are metamorphosed into the protometra. In 

 the female there are not such converging growths between the 



o O o 



duct f and the gland c : the duct f shrinks with the Wolffian 

 body, and is reduced to the remnant recognisable in the adult 

 as a ' canal of MalpigmV But the tube, g, rises above the AYolffian 

 body, expands as at e, fig. 590, and afterwards opens at f. As 

 the Wolffian body atrophies, 

 the duct, f, fig. 589, be- 

 gins to be tortuous in the 



o 



male, and becomes ( sperm- 

 duct'; while g shrinks : but, 

 in the female, g widens, 

 and becomes, as in fig. 591, 

 oviduct, c, and uterine horn, 

 b : but the distinction is late 

 in the Ruminant embryo. 



> TTrogemtal organs, foetal Sheep, cccxxi". 



In the human embryo at 



three months, the lower or distal portions of c, c, fig. 592, have 

 dilated and become fused into the uterus, a, which still shows 



590 



