THE VEINS OF THE TRUNK 291 



and receives veins corresponding to its branches, as well as the 

 cephalic. 



The subclavian vein is the continuation upward of the axillary, 

 and runs at a lower level than its artery, from which it is sepa- 

 rated by the phrenic nerve and scalenus anticus, to the inner 

 border of that muscle, to join the internal jugular, forming the 

 innominate. It receives the external jugular, and occasionally 

 the anterior. 



THE VEINS OF THE TRUNK 



The azygos veins are three in number. 



I. The right, or vena azygos major, commences by the right 

 ascending lumbar vein. Ascending to the thorax through the 

 aortic opening and on the bodies of the dorsal vertebrae to 

 the fourth, it arches over the root of the right lung and joins 

 the superior vena cava above the pericardium. It receives the 

 right superior intercostal vein and the remaining right intercostal 

 veins save the first, the left azygos, the right bronchial, and 

 some esophagcal, posterior mediastinal, and pcricardiac veins. 

 Below it communicates with the common iliac by means of the 

 ascending lumbar. 



II. The vena azygos minor inferior vein commences as the left 

 ascending lumbar, and ascends through the left crus and along 

 the spine to the ninth dorsal vertebra. It then crosses to the 

 right, behind the aorta, and joins the vena azygos major. It 

 receives the lower three or four intercostals and some mediastinal 

 veins. 



III. The vena azygos minor superior vein is formed by the 

 fourth intercostal to the eighth inclusive, and joins the large 

 azygos. It receives the mediastinal tributaries, left bronchial 

 vein, and communicates above with the left superior intercostal. 



The intercostal veins lie above the arteries. 



The bronchial veins return part of the blood from the bron- 

 chial arteries. The right joins the vena azygos major; the 

 left, the left upper azygos. 



The spinal venous system is made up as follows: (a) The 

 dorsal spinal veins; (6) the venae basis vertebrae; (c) the anterior 

 longitudinal spinal veins; (d) the posterior longitudinal spinal 

 veins, and (e) the veins of the cord, which run tortuously in pia 

 mater, one larger vein along the anterior fissure. 



