ABSENCE OF THE VENA CAVA INFERIOR 399 
stage when it is already quite large, and the connection with the 
liver is well established. It receives the blood from the pelvic 
limbs through channels which lie at first along the dorsal surface 
of the Wolffian body and then are diverted ventrally to the inter- 
subeardinal anastomosis. In addition to these large channels, 
the Wolffian body shows many small transverse veins which 
encircle its peripheral part as described by Sabin. It will be 
noted further that although the veins of the right Wolffian body 
are drained anteriorly by the posterior cardinal vein, this chan- 
nel is reduced in size and on the left side its continuity apparently 
has been interrupted. 
In the model of the abnormal embryo, no connecting link is 
found between the cardinal and hepatic systems of veins. More- 
over, the posterior cardinal veins are noted as prominent trunks 
along the whole length of the Wolffian body on its dorsolateral 
surface, receiving the veins of the pelvic limbs below and empty- 
ing into the common cardinal veins above. The subcardinals 
of the abnormal embryo are small, and the anastomoses across 
the ventral aspect of the aorta are not large. It would appear, 
therefore, from a study of this embryo that the two sides are as 
yet practically symmetrical. In a case described. by Von Reck- 
linghausen, in a child at birth, there was said to be a persistence 
of both cardinals, each receiving its corresponding renal vein, 
thus, the right cardinal emptied into the vena cava superior and 
the left terminated in the left subclavian. With the exception 
of the three cases of Hyrtl in anencephalic embryos, this is the 
only case of the sort which I have found. If the cardinal veins 
in the abnormal pig embryo should persist throughout, a condi- 
tion similar to these rare cases would result, but it would be 
quite possible for the anterior part of either the right or left 
cardinal to disappear, giving rise to a more familiar type of 
anomaly. Whether, in case a single channel were formed, the 
renal vein from the opposite side would pass dorsal or ventral 
to the aorta would be determined by the fate of the small pre- 
aortic subcardinal anastomoses. ‘The usual course of the renal 
vein in these cases is behind the aorta, but in this specimen post- 
aortic anastomoses have not yet developed. Because of the 
early stage in the production of the anomaly, it is impossible to 
