ABSENCE OF THE INFERIOR CAVA BELOW THE DIAPHRAGM. 11 



region. Such is the opinion of Hochstetter ; and Minot ^ has 

 demonstrated it on pig embryos. Whether the vein running 

 up along the front of the column into the right renal is a part 

 of the right cardinal, and whether its diverging branch be the 

 right spermatic, are questions not to be answered. The system 

 of loops along the side of the column in the lumbar region, 

 connecting, certainly on one side, and probably on the other, 

 with the iliac vein just at the beginning of the internal iliac, is 

 probably a secondary series of anastomoses between the original 

 segmental veins. The connection with the iliacs suggests 

 naturally the lower ends of the cardinals as shown in all dia- 

 grams, but Hochstetter has pointed out, against Kerschner, that 

 this line of vessels is pre-costal, while the cardinals are pre- 

 central. I may further remark that it seems far from certain 

 that the iliacs ever were the original terminations of the 

 posterior cardinals, and that my colleague Professor Minot 

 considers the doubt allowable. 



The one point on which this case differs from all others yet 

 described is the small size of the anomalous vein. Krause 

 alludes to the vein replacing the cava as materially enlarged. 

 In all illustrations that I have seen, the vein is as large or larger 

 than the aorta; while here it is not much larger than the 

 normal azygos. The system of veins at the back of the abdomen 

 does not seem sufficient for the extra work, which possibly was 

 carried on by the plexuses within the spinal canal. 



A study of the instances of this anomaly show that there is 

 a tolerably simple system of classification, which is meant to 

 include only cases of absence of the inferior cava below the 

 diaphragm. First, there are the cases of persistence of both the 

 posterior cardinals ; then, those of the persistence of one of 

 them. This one is almost always the right one. Situs inversus 

 is particularly frequent with this anomaly ; and it must be 

 remembered that persistence of the right or left cardinal with 

 transposition of the viscera is analogous to that of the other, 

 when they are in their proper places. There are several cases, 

 like this one, in which the lower part of the left posterioi 

 cardinal and the upper part of the right one are preserved. 



1 " On the Veins of the Wolffian bodies in the Pig," Proc. Boston Soc. Nat. Hist., 

 vol. xxviii. No. 10, 1898. 



