COMMON BRACHIOCEPHALIC TRUNK 



633 



subcostal artery (A. intercostalis suprema) is the smaller. It passes backward 

 atong the lateral border of the longus colli Avith the sympathetic trunk. It gives 

 off the second, third, and fourth intercostal arteries, and ends at the fifth space 

 where it anastomoses with the first aortic intercostal artery, or constitutes the fifth 

 intercostal artery, or dips into the longissimus muscle. It also gives off spinal 

 branches and twigs to the longus colli and the pleura. The other branch (A 

 transversa colli) is the direct continuation of the trunk. It emerges through the 



Fio. 554. — Topography of Tsobax of Horse, Rioht Side, after Removal of Lung, Pericardium, and Greater 



Part of ^Iediastinal Pleura. 

 1, Right ventricle; 1', left ventricle; 2, right atrium; 2', left atrium; 3, anterior vena cava; 4, posterior vena cava; 

 5, vena azygos; 6, phrenic vein; 7, aorta; 8, right coronary artery; 9, bronchial artery; 9', cesophageal artery and vein; 

 10, first aortic intercostal artery and vein; 11, right pulmonary artery; 12, pulmonary veins; 13, right brachial vessels; 

 14, dorsal vessels; 14', subcostal vessels; 15, deep cervical vessels; 16, vertebral vessels; 17, inferior cer\'ical artery; 

 18, internal thoracic vessels: 18', musculo-phrenic artery; 19, bicarotid trunk; 20, common carotid arteries; 21, jugu- 

 lar vein; 22, thoracic duct; 23, right vagus; 23', cesophageal continuations of vagi; 24, right recurrent nerve; 25, right 

 phrenic nsrve (part which crosses pericardium indicated by dotted line) ; 26, sympathetic trunk; 27, great splanchnic 

 nerve; 28, oesophagus; 29, trachea; 30, right bronchus; 31, left lung; 32, basal border of right lung indicated by dotted 

 line; 33, mediastinal pleura; 34, diaphragm; 35, diaphragmatic Une of pleural reflection; 36, intercostal muscle; 37, 

 longus colli; 38, psoas; 39, interspinous ligament; 40, supraspinous ligament; 41, funicular part, 41', lamellar part, of 

 ligamentum nuchge. 



dorsal end of the second intercostal space, passes across the longissimus costarum and 

 longissimus dorsi toward the withers, and divides into several diverging branches. 

 An anterior branch passes upward and forward between the splenius and complexus 

 and anastomoses with branches of the deep cervical artery; the others ascend on 

 the dorso-scapular ligament under cover of the serratus ventralis and rhomboideus 

 to the withers, supplying the muscles and skin of this region. 



The left dorsal artery sometimes arises with the deep cervical by a common trunk; this 

 arrangement is usual on the right side, and there may be a common stem for the dorsal, deep cervi- 

 cal and vertebral arteries. Occasionally the artery arises from the brachiocephalic trunk. Some- 

 times it emerges through the third space. The subcostal may arise independently behind the 

 dorsal or from the deep cervical artery. 



2. The deep or superior cervical artery (A. cervicalis profunda) arises in front 

 of the dorsal or by a common trunk with it. It crosses the cesophagus (left side), 



