534 



THE BLOOD-VASCULAR SYSTEM 



for the nerve. The vein, which is larger than the artery, lies to the lateral side, 

 and somewhat overlaps it. The vagus nerve lies behind and between the two 

 vessels. The arter}^ on the right side measures about 9.5 cm. (3f in.) ; on the left 

 side, about 12 cm. (4f in.) in length. 



Fig. 444. — The Collateral Circulation after Ligature of the Common Carotid and 



Subclavian Arteries. 

 (A ligature is placed on the common carotid and on the third portion of the subclavian artery.) 



Right anterior cerebral 



Internal carotid 

 Right posterior cerebral ■ 



Occipital 

 Descending branch of occipital 



External carotid 



Superficial branch of descending 

 occipital 



Deep branch 

 Ascending cervical 



I 



Transverse cervical 



Descending branch 



Acromial branch 



Subscapular branch 



Supraspinous 

 branch 



Anterior circumflex 



Infraspinous branch 

 Posterior circum- 

 flex 

 Lateral thoracic 



Subscapular 



Circumflex scapulai 



Infrascapular 



Subscapular 



Left anterior cerebral 

 Anterior communicating 



Posterior communicating 

 Left posterior cerebral 



Basilar 



Anterior spinal 



Vertebral 

 External maxillary 

 Lingual 



Superior thyreoid 



Inferior thyreoid 



Common carotid 



Thyreo-cervical trunk 

 Costo-cervical trunk 



Innominate 

 Superior intercostal 

 -Left common carotid 

 Left subclavian 

 Superior thoracic 

 Internal mammary 



Anterior intercostal 



First aortic inter- 

 costal 

 Second aortic inter- 

 costal 



Anterior intercostal 



.Third aortic inter- 

 costal 



Relations.— In front tlic artery is covered by the skin, superficial fascia, platysma, and 

 deep fascia, and i.s inoic or 1(;hs overlapped by the storno-mastoid muscle. At the lower part 

 of the neck it is covered in addition by llie .storno-liyoid and sterno-thyreoid muscles, and is 

 cmssed \>y th(^ arilcrior juKular vein and is often overlapped l)v the thvreoid Kland. Opposite 

 the cricoid cartilage it is crossed oblitjiiely by the onio-hyoid muscle, and, above this spot, by 

 the superior thyreoid vein, and tiie stcrno-mastoid artery. Along tlie anterior border of the 

 sterno-mastoid there is a communicating vein between the facial and anterior jugular veins, 

 which, as it crosses the line of the carotid artery, is in danger of being wounded in the operation 



