ORIGIN OF THE RENAL ARTERY 199 



kidney, which hes immediately below the level of the recon- 

 struction. From the upper end of the longitudinal vessel, on 

 the left of the figure, a twig passes upward, possibly the future 

 inferior phrenic artery. On the right side of the figure a simi- 

 lar vessel comes from a mesonephric artery, which also has two 

 small suprarenal branches, thus showing an unusual condition. 

 This same mesonephric artery is connected not only with a supra- 

 renal trunk but also with the coeliac axis. Smaller aortic 

 branches are shown, one ventral between the coeliac axis and the 

 superior mesenteric artery, others lateral. 



The permanent renal artery would have included the main 

 trunk from aorta to kidney, arising normally in this case at the 

 level of the second lumbar arteries, and would have had suprarenal 

 branches. A spermatic branch would have been impossible in 

 this embryo on the right side of the figure, highly improbable 

 on the other, though a roundabout connection between kidney 

 and mesonephric artery does exist. One can readily see, however,, 

 that if more of the plexus had been retained, spermatic branches 

 would have been easily possible. The origin of the renal artery 

 from the coeliac axis can also be imagined in this case, and 

 similar anastomoses between lateral or mesonephric vessels 

 and the superior mesenteric artery would account for a renal 

 branch of the latter vessel. Dorsal connections of the suprarenal 

 arteries with the body-wall or with true dorsal segmental arteries 

 can be conjectured as a persistence or extension of the plexus. 

 The permanency of all such connections, however, must depend 

 on the occlusion of more favorable channels. 



SUMMARY 



1 . The anomalies of the renal artery depend on vessels present 

 in the embryo before the aorta and its larger branches develop 

 mesodermal coats (10-15 mm. embryos). There are no 4ate 

 branches.' 



2. Certain anomalies are due to the persistence of the early 

 renal blood supply most frequently seen with pelvic kidneys; 

 i.e., the renal artery as a branch of the iliac, inferior mesenteric 

 or middle sacral arteries, or from the aorta below the inferior 



