46 CHARLES F. W. McCLUEE AND GEORGE S. HUNTINGTON 



veins. Such being the case, if the right supracardinal (B in 

 fig. 1) had persisted in the variant (fig. 61) in place of the 

 right posterior cardinal, the relations of the cava to the ureter 

 and the aorta would in the variant and the marsupial have 

 been exactly the same. 



Another example of a case in which the cardinal collateral 

 vein of the embryo (C.C.) has been retained in an adult cat is 

 shown in figure 62. Also, a case identical to this has been 

 described and figured by Johnston ('13, p. 235), as occurring 

 in adult man. While these two cases are not so typical as 

 that shown in figure 61, nevertheless they represent instances 

 in which a vein, extending ventral to the aorta between the 

 left iliac and the caval veins (right supracardinal, Type B), 

 has been derived from the ventral portion of the embryonic 

 circumumbilical venous rings (C.C. in fig. 1). An analysis of 

 figure 1 clearly shows the possibilities which exist as regards 

 the persistence of such a ventral venous channel as that 

 shown in figure 62. Its origin from the cardinal collateral 

 vein of the embryo is the only plausible explanation of its 

 presence in the adult cat and in man. 



Another example of the Marsupial Type has more recently 

 been described and figured for adult man by "Wicke ('27). 7 

 In this case (fig. 63), a periureteric venous ring, through 

 which the ureter passes, is present on the right side (Type 

 AB) ; in addition to this venous ring, however, there is pres- 

 ent a persistent cardinal collateral channel, represented by 

 the left common iliac vein (V.il.c.s.}, which passes ventral to 

 the right common iliac artery (A.il.c.d.), to become directly 

 continuous with the right posterior cardinal vein (V.cv.v.). 



7 "fiber einen Fall von Inselbildung im Bereiche der hiiiteren Hohlvene (Vena 

 cava posterior) und Durchtritt des rechten Harnleiters beim Erwachsenen. Zeitsch. 

 fur Anat. und Entwicklungsgesch., Bd. 84, S. 524-533. 



This paper did not appear until after Doctor Huntington's death. Also, since 

 1927, two other important papers have appeared dealing with atypical conditions 

 of the vena cava posterior : 



Maxwell, E. V., and Erwin, G. S. 1928. Four cases of anomalous inferior vena 

 cava with an explanation of their development. Jour. Anat., vol. 62, pp. 184-197. 



Kadletz, M. 1928. "fiber eine Missbildung im Bereich der Vena cava caudalis 

 beim Hunde. Zeitsch. fiir Anat. und Entwicklungsgesch., Bd. 88, S. 385-396. 



