94 



COMPARATIVE ANATOMY 



Subintestinal Veins: 



Caudad to this connection a pair of subintestinal veins (Fig. 450) 

 run toward the tail end on the ventral side of the digestive canal. These 

 fuse together into a medial tube just behind the anal opening, which ex- 



Fig. 450. 



Diagrams to show the development of the postcayal vein in the cat. The 

 cardinal system of veins is cross-hatched, the subcardinal veins closely stippled, 

 the hepatic veins are indicated by cross, vertical, and oblique hatching combined, 

 the supracardinal veins by open stippling, and the renal cottar by vertical hatching. 



A, early stage, showing the anterior and posterior cardinal veins, a, b, c, 

 the common cardinal vein d, the subcardinal veins /, and the outgrowth e from the 

 hepatic veins of the liver. B, next stage, showing the union of the hepatic 

 outgrowth e with the subcardinal veins /, to form the proximal part of the 

 postcaval vein ; the two subcardinals have united with each other at h. 



C, the anterior part of the posterior cardinal vein 6 has separated from the 

 posterior part c, c now being the renal portal vein ; the postcaval vein is seen to 

 be formed of the hepatic vein e, the right subcardinal /, and to be united by meajis 

 of the two subcardinals below h with the renal portals c. 



