ANTERIOR VENA CAVA. 



443 



the thorax. This large but short vessel is situated at the anterior 

 part of the thorax, between the layers of the anterior mediastinum, 

 below the trachea, and to the right of the anterior aorta, to which 

 it corresponds. It is formed between the first pair of ribs, by the 

 union of the two jugular and two brachial veins, receiving the 

 internal thoracic, vertebral, superior cervical, dorsal, and the great 

 vena azygos. 



The Internal thoracic, Vertebral, and Superior cervical 

 veins, are satellites of, and counterparts in distribution to, their 

 corresponding arteries. 



Fig. 107. 

 Thorax opeaeJ on the right side to show the heart and veins. A, Heart, with left coronary vein ; 

 1 1, Anterior cava ; 2, Postericr cava ;* a, Lsf t brachial ; 6, Right brachial cut ; c, Left jugular ; 

 d, Internal thoracic ; d', A mediastinal vein : e, Right vertebral ; /, Dorsal and superior cervical 

 veins discliarging together ; /, Eight superior cervical ; f, Right dorsal ; o, Vena azygos ; g', (Eso- 

 phageal ; g", Bronchial ; g"' g'", Intercostals. 



The Dorsal vein follows the same course as the dorsal artery, 

 receiving also several intercostal branches, the right one returning 

 the blood from the second to the fifth intercostal spaces ; the left, 

 sometimes called the lesser vena azygos, is prolonged as far back 

 as the eleventh or twelfth intercostal space, receiving blood from 

 the intercostal veins of all the spaces it crosses. 



On the right side the vertebral, superior cervical, and dorsal 

 veins may reach the vena cava separately, whereas those on the 

 Jeft enter by a common trunk. 



