ORIGIN OF THE RENAL ARTERY 195 



connected by longitudinal anastomoses, but unconnected with 

 the mesonephric or dorsal segmental arteries for reasons stated 

 above. From the longitudinal strands of the plexus branches 

 pass to the body-wall, which by 10.0 mm. (H.E.C. No. 155) 

 have become long vessels. In this same embryo branches from 

 the lower end of the plexus have entered the kidney. The longi- 

 tudinal anastomosis and one of its aortic connections are the 

 vessels figured by Lewis. The lateral branches to the body- 

 wall are not shown by him, but nevertheless form a permanent 

 connection; one at least remains as a normal branch of the renal 

 a tery in adult rabbits. This is mentioned by Gerhardt (14) 

 in the,following description, p. 245: "From each renal artery, near 

 its root springs a small (the 12th) intercostal artery." This is 

 obviously not a true intercostal with dorsal connections, but must 

 run in front of the psoas muscles and thus be comparable with the 

 'false lumbar' arteries already referred to. Spermatic branches 

 of the renal artery are not described in the rabbit, to my knowl- 

 edge, and are not to be expected because of the early separation 

 of the plexus from the mesonephric arteries. 



I think the detailed description of the origin of the renal artery 

 in the cat and the rabbit is sufficient to show how the variations 

 in the different classes arise. The pig makes use of a lateral 

 aortic branch, or, as is shown in figure 5, of a branch of the 

 dorsal segmental artery. In the sheep a lateral aortic branch 

 is commonly enlarged. In both the connection of the plexus 

 with the kidney is made early, and originally at the superior 

 pole of the organ. 



It should be noted that in all classes of mammals the early posi- 

 tion of the kidney, before it has escaped from the crotch of the 

 lower bifurcation of the aorta by migrating upward and backward, 

 as described by Pohlman (15) and by Lewis and Papez (16), 

 is nearer to the mesonephric arteries, because more ventral, 

 than after this escape. My observations, contrary to those of 

 Broman (4) in his paper on the renal portal system, show fre- 

 quent early mesonephric branches to the kidney, some in use, 

 some partially obliterated, in all the animals examined. When 

 no larger branches are present, certain of the glomerular efferent 



