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COMPARATIVE MORPHOLOGY OF VERTEBRATES 



the suprarenal and gonad of that side), and all the blood from the posterior part 

 of the body is returned by the right postcardinal and the postcava, which appear 



Fig. 350. — Development of posterior veins of rabbit, after Hochstetter. C and D 

 represent only the hinder part of the whole shown in A to C. In B the veins for the 

 postcaval-subcardinal system have tapped the postcardinal veins, which in C have lost 

 their connexion with the anterior part and empty now through the postcava exclusively. 

 In E the left posterior postcardinal is entirely lost, i, ischiadic vein; ie, external iliac; 

 i, jugular; mt, metanephros (kidney); p, postcava; pc, postcardinal; s, subclavian; sc, 

 subcardinal; sr, suprarenal; u, ureter. 



Fig. 351. — Development of the anterior veins of a mammal. A, earlier stage, to be 

 compared vnth. fig. 350 C; B, definitive condition of adult, a, azygos; c, coronary; e, i, 

 external and internal jugular; ha, hemiazygos; il, iliac; in, innominate; p, postcava; pc, 

 postcardinal; pre, precava (superior vena cava) ; si, superior intercostal veins. 



(fig. 351, A) as if they arose from a union of the iliac veins. Correlated with 

 these changes in the venous system and the impossibility of venous blood enter- 



