THE MAMMALIAN VENA CAVA POSTERIOR 43 



2. Ill mammals other than man, it has been described in 

 the cat, by Huntington and McClure, Pearl ('08), and Hunt 

 ( '19) ; in the dog, by Ponsot ( '56), Korosy ( '10), and Cooper 

 ('20) ; in the deer (Cervus tarandus ) , by Barkow ('66) : and 

 in the guinea-pig (Cavia) by Phisalix ('98). 



17. Persistence of renal collar (circumaortic venous ring at 

 level of renal veins] 



See renal collar in figure 1. Figure 59, man (Huntington Collection) 



The renal collar is a term used by Huntington and McClure 

 to designate an extensive embryonic venous ring, which, like 

 a collar, encircles the aorta, at the level of the renal veins. 

 In the embryo of the cat (fig. 1) the renal collar is formed 

 ventrally by the intersubcardinal anastomosis (Int.Subc. 

 Anast.) and the right and the left subcardino-posterior car- 

 dinal anastomoses (Sub c. PC. Anast.) ; laterally, by the right 

 and the left subcardino-supracardinal anastomoses (Subc. 

 Sprc. Anast.) ; and dorsally, by the intersupracardinal 

 anastomosis (Int. Sprc. Anast.) between the supracardinal 

 veins. The renal collar serves in the embryo as a com- 

 mon meeting place for all main axial venous channels 

 and is a region toward which blood is directed from the sys- 

 temic veins to the heart, by way of the liver, through the pre- 

 renal division of the vena cava posterior (P.Subc. and P.Hep., 

 fig. 1). In transforming from the embryonic to the adult con- 

 dition, the renal collar early loses its ring-like character, and 

 only a portion of it is retained in the adult cat, where it 

 enters into the formation of the left renal vein (Subc.Pc. 

 Anast.Sin) and of a small segment of the vena cava posterior 

 (Subc.Sprc.Dext., fig. 1). For further details the reader is 

 referred to the article by Huntington and McClure ('20), on 

 "The development of the veins in the domestic cat." 



In figure 59 we have represented an instance in which the 

 renal collar, in essentially its embryonic condition, has per- 

 sisted in adult man. In two other cases observed in man, one 

 shown in figure 35 and the other figured by Oberndorfer ( '03), 

 the aorta is encircled by a venous ring, but not in so typical 



