108 



THE HEART AND CIRCULATION. 



divides into the right common carotid and right sub- 

 clavian. 



The common carotids pass up the neck behind the 

 sterno-cleido-mastoid muscles in a line from the sterno- 

 clavicular joint to a point mid- 

 way between the mastoid process 

 and the angle of the lower jaw 

 and divide opposite the upper 

 border of the thyroid cartilage 

 into the internal and external 

 carotids, of which the former with 

 its branches supplies the anterior 

 part of the brain, the eye and 

 forehead, and the latter the neck 

 and face. 



The subclavian is the artery of 

 the upper extremity but its 

 vertebral branch goes to the 

 brain, where with its fellow it 

 forms the basilar artery, whose 

 branches together with the 

 branches of the internal carotid 

 form the circle of Willis at the 

 base of the brain. Other branches 

 of the subclavian are the thyroid 

 axis, with branches to the neck 

 and shoulders; the internal mam- 

 mary, with branches to the chest 

 walls, mediastinum, and dia- 

 phragm, such as the musculo- 

 phrenic and superior epigastric; 

 and the superior intercostal. At 

 FIG. 44. The aortjB and their the lower border of the first rib, 

 over which it passes, the name 



axillary is substituted for subclavian, while at the lower 

 border of the axilla, where it starts down the arm, it 

 is called the brachial artery. At the elbow the brachial 

 divides into the radial and ulnar arteries. The axillary 



