WOLFFIAN BODIES 



307 



ology, Vol. 2). Except for its duct, it entirely disappears in very young 

 embryos (5 mm.). All the renal organs pronephros, Wolffian body (or 

 mesonephros) , and kidney (or metanephros) are developed from the 

 nephrotomes. They are all composed of mesodermal tubules, each of 

 which is in close relation with a knot of capillary blood vessels derived from 

 branches of the aorta. Such a knot of vessels is a glomerulus, and certain 

 products are eliminated from the glomerulus into the tubules to form the 

 urine. 



Development of the Wolffian Body and Wolffian Duct. The general 

 relations of the neplirotome to the mesodermic somites and to the coelomic 



mes.seg'. 



,W.d. 



neph. 



nch. 



B C 



FIG. 303. A, TRANSVERSE SECTION OF A RABBIT EMBRYO OF NINE DAYS; B, HUMAN EMBRYO, 4 MM.; 



C, HUMAN EMBRYO. 10 MM. 

 mo, Aorta; c., posterior cardinal vein; coe., ccelom; gl., glomerulus; g. r., genital ridge; int., intestine; mes. 



mesentery; mes. seg., mesodermic somite; my., myotome; nch., notochord; neph., nephrotome; s-c. v. 



subcardinal vein; si., sinusoid; sy., sympathetic nerves; u. v., umbilical vein; W. d., Wolffian duct 



W. t., Wolffian tubule. 



epithelium have already been briefly discussed (p. 41). A nephrotome 

 from a young rabbit embryo is seen in section in Fig. 303, A, together with 

 its elevation which contributes to the formation of the Wolffian duct. The 

 nephrotome here shown is from one of the anterior segments and belongs 

 with the pronephros. 



In human embryos, according to Felix, pronephric tubules are formed 

 from the seventh to the fourteenth segments, and perhaps from those 

 further forward. The elevations to which these nephrotomes give rise 

 turn posteriorly and unite with one another to form the Wolffian duct. 

 This is at first a solid cord of cells which grows posteriorly in the trough 



