4 CONTENTS 



16. Persistence of embryonic supracardinal system of veins to form 



a continuous system of vessels in the lumbar and the thoracic 

 regions, by means of which blood from the iliac region can be 

 conveyed directly to the heart, without passing through the 

 liver 39 



17. Persistence of renal collar (circumaortic venous ring at level of 



renal veins) 43 



18. Persistence of subaortic plexus (embryonic cardinal collateral 



veins). Marsupial Type of vena cava posterior 44 



VII. Table showing relative frequency with which the different Types of 

 vena cava posterior have been observed to occur in the adult 



cat and in man 48 



VIII. General conclusions 48 



IX. Literature cited 49 



X. Abbreviations 56 



XI. Plates . 57 



