56 DISSECTION OF THE VASCULAR SYSTEM. 
CO THE HRPATTIC PORTAL EASY STL OF AVES. 
The Portal Vein is the large vein lying in the mes- 
entery which collects venous blood from the stomach, 
pancreas, spleen and intestines, and passes into the 
under side of the liver. Within this organ it again 
breaks up into capillaries, the blood from which is 
finally collected into the hepatic veins which empty 
into the post-cava. The portal can easily be found on 
the under side of the liver; it is formed from two 
large branches, one from the intestines and one from 
the spleen, pancreas and stomach. It breaks up into 
branches which enter the different lobes of the liver. 
DY VEINS, BELONGING “LO ti SYSTEM OF. 
LH EE PRAEACAYV A, 
1. The Pre-cava (superzor vena-cava). A descrip- 
tion of this vein has been given in the chapter on 1 the 
dissection of the thoracic viscera. 
2. The Vena Azygos. Make out again the course 
of this vein, and the point where it opens into the 
pree-cava. 
32 he Vertebral Veins. ihe vein on- the’ rieht 
side opens into the cava anterior to the azygos. ‘Trace 
it back to its emergence from the vertebral canal of 
the spinal column. The vein on the left side opens 
into the left brachio-cephalic or innominate vein. 
They bring back blood from the brain, etc. 
4. The Sternal Veing. “he vein- on the neht sides 
opens into the pre-cava anterior to the vertebral. 
On the left side it opens into the brachio-cephalic be- 
yond the vertebral. They bring back blood from the 
sternum and the anterior wall of the thorax. 
