TIM: 01 mi: MIDDLE GUM LAI : 399 



sinus nro-eiiitalis the urinary fluid ami the male or female .--xual 

 products. 



it far as regard.- the special eondit i >n- in Man. tin- allai. 

 remains in his case very small dig. !"-. ~> "^ .-ind pn>- sss a lumen 

 ill tin- region of the body-cavity */////. whereas in the umbilical cord 

 and between the remaining fetal membram s only its connective 

 ti. in- part, together \\ith tlie blood- v--.-el-. which shares largely in 

 the development t' tin- placenta. im>\\s fuitht-r. In the second 

 montli its hollow part, lying on th- front wall of the abdomen. 

 becomes a spindle-shaped body .<. lt> middle i-nlar^" 



becomes tin 1 urinary hlaildt-r ( , ), it- upward prnlnn^'at ion, which 

 tvachrs to the navel, is called urachus ( 5 ), the other end (/"/) is the 

 Minis tiroio-iii'talis. The urachu> degenerates during eml ryonic lit'. 



furnislies a connect ive-ti>sue cord, the ligament um \e-icoumhilicalf 

 inediuni. which extends from the apex of the bladder (tiir. L'l'.i ///*/') 

 to the navel, ami often in the lii ,t'ter lurth still contaii. 



epithelial cord, a remnant of the original epithelial canal. 



Afl is well known, the ureters (figg, L'J'J 3 and iMU /</') in the adult 

 open close together at the posterior surface of tin- uiinary l>]adler 

 4). In very young embryos this is not the ca>o nt iir>t, for the 

 two ureters arise from the posterior part of the mesoiu-phric duct, 

 and this opens into the sinus urogrnitalis. \\nt this condition is 

 soon altered. The ureter splits off from the mesonephric duct, 

 and comes to open independent ly into the posterior wall of the sinus 

 urogenitalis. fiom which it afteruards becomes gradually rem. 



its oriliiv. M i' were, cieeps higher up on the posterior wall of the 

 bladder. Like the change in the position of the sexual glands, we 

 must also conceive of this shifting as produced by processes of growth 

 in Mich a way that especially the tract between mesonephric duct 

 and ureter, which is at first small, increases in >i/.e, and t hereby 

 produces the apparent upward migration of the opening of the 

 ureter. 



hi tho sixth week the cloaca in .Man undergoes alterations which 

 are connected with the development of the external sexual organ-. 

 The cloacal depression, which in earli 



lissure-like, atteruards becom-- itiif. _.':'<> /! \ surionnded by a rin--- 

 like fold, the genital ri- : and there al- 



portion a growth of CXmnective tlflSUe, which produce- the externally 



protruding genital eminence Along the lower surface ot the 



latter there is formed al thesametin -/M, which extend* 



downward to tlu- cloaca, of which it is, ;i- it \\ere. the continuatiuii. 



