194 JOHN LEWIS BREMER 



The plexus here is still connected with the mesonephric arteries, 

 and no enlargement of the lateral aortic branches is found, so 

 that the right side of this embryo is in the same condition as both 

 sides of the embryo of 10.7 mm. 



The permanent renal artery in the cat is thus formed partly 

 from a suddenly enlarged but long present lateral branch of the 

 aorta, partly from the longitudinal meshes of the periaortic plexus, 

 and partly from branches from the lower end of this plexus to 

 the upper pole of the kidney; the connections are present before 

 10.7 mm. 



Anomalies to be looked for in the cat, easily explicable by the 

 history as thus shown, are, first, double or multiple renal arteries 

 from the aorta, since there are several lateral connections from 

 aorta to plexus, and, second, a spermatic or ovarian branch of 

 the renal artery. This latter would require merely the persist- 

 ence of the original mesonephric union with the plexus, and a 

 reversal of the blood current through it, so that the mesonephric 

 plexus from which the spermatic artery sprouts would receive its 

 blood through the renal artery and the lateral plexus; the meso- 

 nephric trunks might then all disintegrate. Spermatic branches 

 of the renal arteries are mentioned as occasionally present in 

 the cat by Reighard and Jennings. 



The renal artery in the rabbit has been figured by Lewis (13) 

 in reconstructions of embryos of 11.0 mm., 14 days (H.E.C. No. 

 No. 1327), and 14.5 mm., 14 days, 18 hours. (H.E.C. No. 143), 

 in his paper on the development of the vena cava inferior. 

 Though hardly referring to this artery in the text, he thus correct- 

 ly represented it in embryos j^ounger than those in which it had 

 then been reported. It is shown as a longitudinal vessel, reach- 

 ing the kidney at its caudal end, attached near the middle of its 

 length, in the 11.0 nnii. embryo, bj'' a vessel springing from the 

 aorta midway between the dorsal segmental arteries and the 

 mesonephric arteries. With more detailed study of rabbit 

 embryos with this point of view, it is possible to find the periaortic 

 plexus present verj^ early, but it is partially lost in embryos of 

 8.0 mm. to 9.0 mm., leaving only the lateral sprouts from the 

 aorta (cf. fig. 2). There are many of these in the lumbar region. 



