38o 



COMPARATIVE ANATOMY 



Heart 



- Ant. Cardinal 



Developing 



Subcardinal 



Plexus in 



fleson. 



Right— 

 Subcord 



Fbat Card. 

 Iliac - 



Fig. 320. — Diagrams illustrating stages in the development of the systemic veins 

 of the pig. The cardinal and omphalomesenteric veins are shown in black, the sub- 

 cardinal system is stippled, the supracardinals are horizontally hatched, and vessels 

 arising independently of these three systems are indicated by small crosses. A , Ground 

 plan of the veins of a young mammalian embryo; B, Cross section (at level of arrow in A) 

 showing dorso- ventral relations of the various veins; C, Diagrammatic plot of veins of 



