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 Soulié.) The com- 
parative embryological investigations, strongly support this view. 
Origin of the Cortical Cords. According to Soulié, 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 
y and fill the space on the medio-dorsal aspect 
of the Wolffian body, and then come secondarily into relation 
cords grow rapid 
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 Soulié, 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 ; 
