540 Wisconsin Academy of Sciences^ Arts^ and Letters. 
two other specimens. The above conditions probably represent 
persisting connections between the subcardinals and the post 
cardinals which were not broken down when the blood from 
the caudal vein /ceased flowing through the kidneys by way of 
'the subcardinals and began to flow by way of the post cardinals 
before they broke down anterior to the kidneys. 
In specimen No. 2 a parietal vein entered the efferent renal 
vein in the mid-kidney region. This is undoubtedly an abnormal 
case as veins in this position have not been described in the 
Ophidia and were not found in any other specimen. It is prob¬ 
ably a persisting connection between the subcardinal veins and 
the parietes. 
One large branch leaves the afferent renal vein and becomes 
the oviducal sinus. Blood may flow through this from the caudal 
vein to the heart by way of the vena cava without passing 
through any portal capillaries (Fig. 4). 
VC AA AV RER LER X 
The left oviducal sinus, from the left side. AA, adrenal artery; AD, 
left adrenal body; AR, afferent renal vein; AV, adrenal portal veins; 
K, kidney; LER, left efferent renal vein; O, ovary; OA, ovarian arteries; 
OS, oviducal sinus; RER, right efferent renal; VC, vena cava; X, ab¬ 
normal connection between the efferent and the afferent renal veins. 
The origin of the inferior mesenteric vein from the afferent 
renal veins is described in connection with the portal vein. 
The Vena Cava 
The vena cava originates from the junction of the two effer¬ 
ent renal veins near the anterior end of the right kidney and 
runs forward to the heart. It may receive blood from the cau¬ 
dal vein by any one of the following routes: (1) through the 
kidneys, (2) by way of the oviducal sinus, (3) by an occasional 
direct connection between the afferent and efferent renal veins, 
(Figs. 3, 4). 
The vena cava receives blood from the parietes by way of 
the adrenal bodies. From one to three veins leave the dorsal 
