ANATOMY OF A 17.8 MM. HUMAN EMBRYO 81 



tion. The cephalic two have a common stem of origin from the 

 aorta. 



The first passes through the caudal part of the suprarenal 

 gland to the Wolffian body. It presumably becomes the inferior 

 suprarenal branch of the left renal. 



The second skirts the caudal part of the suprarenal anlage^ 

 passing dorsal to the left suprarenal vein (left subcardinal) , and 

 ends in the region medial to the metanephros of that side. It 

 may be concluded, therefore, that this artery (including the 

 common trunk referred to above) becomes the left renal. 



The corresponding artery (renal) on the right arises from the 

 aorta dorsal to the left renal vein (renal anastomosis) and ex- 

 tends to the Wolffian body, passing dorsal to the subcardinal seg- 

 ment of the inferior vena cava. 



Broman ('08) finds that the renal arteries take origin from 

 the 21st or 22nd aortic segment. 



The third mesonephric artery is small and, hence, of little 

 moment. The corresponding one on the right passes in a strand 

 of mesenchjana through the inferior vena cava (i.e., the supra- 

 ureteral channel). 



The fourth (A.sp.i.) is of considerable caliber. It takes origin 

 at the level of the 21st dorsal intersegmental arteries, dorsal to 

 the termination of the left suprarenal vein, and extends caudad„ 

 lateral to the anlage of the corresponding spermatic vein, to the 

 Wolffian body. In the W^olffian body it supplies several glomeruli,, 

 lying adjacent to the most prominent part of the genital ridge. 



The corresponding artery on the right arises from the aorta 

 dorsal to the renal anastomosis. It extends ventral to the vena 

 cava inferior (i.e., the supra-ureteral channel) and caudad along 

 the lateral side of the anlage of the right spermatic vein to the 

 Wolffian body. 



These arteries, from their relations, the author believes, are 

 the embryonic representatives of the internal spermatic (ova- 

 rian) arteries of the adult. 



Broman ('08) finds that usually the spermatic arteries arise 

 from the 22nd aortic segment. 



THE AMERICAN JOURNAL OF ANATOMV, VOL. 17, NO.l 



