ANTERIOR VENA CAVA. 



443 



the thorax. Thia large but short vessel is cituated 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. 



Fjo. 2C7. 

 Thorax opened on the right side to show the hc&rt aad veins. A, Heart, with left coronary vein ; 

 1 1, Aaterior cava ; 2, Posteficr cava ,» a, Lsft brachial ; 6, Eight brachial cut ; c, Left jugular ; 

 d. Internal thoracic ; d! , A mediastntJ vela ; t, Bight vertebral ; /, Dorsal and superior cervical 

 ■veins discharging together ; /, Bight suTierlor cervical ; /", Eight dorsal ; g. Vena azygos ; g', CEso- 

 phageal ; g". Bronchial ; (/"' £/'", Intercostals. 



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

 receiving also several intercostaJ 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 

 -left enter by a common truiik. 



