THE URINOGENITAL SYSTEM 405 



cortical and medullary cords have a common origin from the 

 mesenchyme; (2) that they have a common origin from the 

 peritoneal epithelium; (3) that the origin of the cortical and 

 medullary cords is absolutely distinct, the former being derived 

 from the sexual cords by way of the capsules of the renal cor- 

 puscles and the latter from the sympathetic ganglia; (4) that 

 their origin is distinct, but that the cortical cords are derived 

 from ingrowths of the peritoneum, and the medullary cords from 

 sympathetic ganglia. The first view may be said now to be 

 definitely abandoned, and no one has definitely advocated a 

 common epithelial origin since Janosik (1883). Thus it may 

 be regarded as well established that the two components have 

 diverse origins, and it seems to the writer that the fourth view 

 above is the best supported. (See Poll and Soulie.) The com- 

 parative embryological investigations, strongly support this view. 



Origin of the Cortical Cords. According to Soulie, the 

 cortical cords arise as proliferations of a special suprarenal zone 

 of the peritoneum adjacent to the anterior and dorsal part of 

 the germinal epithelium. This zone is distinguishable early on 

 the fourth day, and begins about half a millimeter behind the 

 glomeruli of the pronephros, extending about a millimeter in a 

 caudal direction. Proliferations of the peritoneal epithelium are 

 formed in this zone, and soon become detached as groups of epi- 

 thelial cells lying in the mesenchyme between the anterior end 

 of the Wolffian body and the aorta. Such proliferation continues 

 up to about the one hundredth hour or a little later, and a second 

 stage in the development of the cortical cords then begins: The 

 cords grow rapidly and fill the space on the medio-dorsal aspect 

 of the Wolffian body, and then come secondarily into relation 

 with the renal corpuscles of the latter and the sexual cords. 



According to Semon and Hoffmann the relation thus estab- 

 lished is a primary one, that is to say, that the cortical cords 

 arise from the same outgrowths of the capsules of the renal cor- 

 puscles that furnish the sexual cords. Rabl agrees essentially 

 with Soulie, and it seems probable that Semon and Hoffmann 

 have overlooked the first stages in the origin of the cortical cords 

 of the suprarenal corpuscles. 



During the fifth, sixth, and seventh days there is a very 

 rapid increase of the cortical cords accompanied by a definite 

 circumscription of the organ from the surrounding mesenchyme; 



