THE VEINS 315 



vessels themszlves when empty are difficult to follmv, owing to 

 the thimiess of their walls. If by chance a large vein is cii,t 

 it must he tied immediately to stop the bleeding. 



1. The system of the vense cavae. 



a. The r ght antrrior vena cava has been already 

 seen. It is formed by the union of the jugular 

 and subclavian veins, immediately in front of the 

 first rib. 



i. The azygos caidiaal ve n is a median vein which 

 runs forwards in the mid-dorsal Hne of the 

 thorax, lying close to the vertebral column 

 and along the right side of the aorta. It 

 receives branches from the posterior seven 

 or eight intercostal spaces of both sides of the 

 body. Opposite the level of the auriclts it 

 passes roimd the right side of the oesophagus 

 and trachea, to open into the vena cava close 

 to the auricle. 



ii. The right anterior intercostal vein is a small 

 vein returning blood from the anterior four or 

 five intercostal spaces of the right side, and 

 opening into the vena cava just in front of the 

 azygos vein. 



iii. The right internal mammary vein runs for- 

 wards on the inner surface of the ventral 

 thoracic wall, near the middle hne, and opens 

 into the vena cava opposite the iirst rib. 



iv. The right subclavian vein returns blood from 

 the fore-limb and shoulder. 



v. The right external jugnlar vein is a large vein 

 running along the side of the neck. It is 

 formed in front by the union, just behind the 

 angle of the jaw, of the anterior and posterior 

 fac al veins, returning blood from the face and 

 ear. 



vi. The right internal jugnlar vein is a small vein 

 returning blood from the brain, and running 



