42 CHARLES F. W. McCLURE AND GEORGE S. HUNTINGTON 



cava inferior which extends between the hepatic veins (Vv. 

 hepaticae) and the renal level had not developed, an essen- 

 tially similar condition would then prevail, as is shown in 

 figures 56, 57, and 58. An examination of figures 55 to 58, 

 inclusive, shows variations in the extent to which the origi- 

 nally bilaterally symmetrical supracardinal veins of the em- 

 bryo may be carried into the adult. In figure 54 the supra - 

 cardinal system has been carried into the adult in essentially 

 its embryonic form; in figures 55 and 56 the right and the 

 left supracardinals are present in the lumbar region, while 

 in the thoracic region only the caudal half of the left and 

 the cranial half of the right supracardinal have been re- 

 tained. In figure 57 the right supracardinal along its entire 

 extent has been carried into the adult stage. In this instance 

 a considerable portion of the left thoracic supracardinal has 

 entered into the formation of the left renal vein. 



The occurrence of variants of this character in the adult cat 

 and in man serves as a complete confirmation of the presence 

 in the embryo of a supracardinal system of veins, which con- 

 stitutes a morphological unity, distinct from that of the 

 embryonic posterior cardinal veins. 



An examination of the literature shows that an atypical 

 condition of the veins, which has been designated by previous 

 writers either as 'absence of inferior vena cava' or as 'per- 

 sistence of posterior cardinal veins,' has been described a 

 number of times as occurring in man and, in a few cases, 

 in other mammals, as follows : 



1. In man, by Abernathy (1793), Barkow ('66), Benb'hr 

 ('04), Bujalsky ('29), Carpentier et Bertaux ('88), Cruveil- 

 hier ('71), Dorsch ('58), Dwight ('01), Goettsch ('20), Gurlt 

 ('19), Herholdt ('32), Hochstetter ('93), Horner ('17), Hyrtl 

 ('39), Kaestner ('00), Lauber ('01), Klob ('59), Kollmann 

 ('93), Lawrence (19), Martin ('62), McWhinnie ('40), 

 Moser ('48), Neuberger ('13), Osier ('78), Otto ('24), Paulus 

 ('42), Quain ('44), Eevell ('03), Tourneux et Wertheimer 

 ( '82), Virchow ( '61), Wertheimer ( '80), Winslow (1775), and 

 Wistar (1827). 



