Chap. XI] 



THE VASCULAR SYSTEM 



209 



Fig. 136. — Portal System of Veins. The liver is turned upward and back- 

 ward, and the transverse colon and most of the small intestines are removed. 

 (Gerrish.) 



or the great azygos vein. These veins receive many tributaries 

 from the thoracic walls and so are often grouped with the thoracic 

 veins. 



It is important to remember that they form a supplementary 



