THE NECK, ANTERIOR. 113 



The artery crosses the phrenic nerve, scalenus anticus 

 muscle, subclavian artery, and brachial plexus. 



Its branches in this part of its course are (a) muscular to 

 the sternomastoid and subclavius ; (ft) nutrient to the 

 clavicle ; (c) the suprasternal ; (d) supra-acromial to these 

 regions ; and (e) the articular to the acromioclavicular and 

 shoulder joints. For the remaining branches, see page 371. 



The Internal Mammary Artery. Fig. 1 8. 



It is given off close to the scalenus anticus muscle from 

 the under surface of the subclavian. It descends directly 

 into the thorax behind the cartilage of the first rib. For 

 its course, relations, branches, and veins, see pages 320. 



The Superior Intercostal Artery. Second Portion of 

 the Subclavian. Fig. 74. 



This branch arises from the back of the subclavian, be- 

 hind the inner border of the scalenus anticus muscle. 



It takes an arched course backward, upward, and then 

 downward into the chest, passing in front of the neck of the 

 first rib. 



From the back of the arch it gives off the deep cervical 

 (profunda cervicis) branch, which passes backward between 

 the transverse process of the seventh cervical vertebra and 

 the neck of the first rib to the back of the neck, where it 

 will be found between the complexus and semispinalis colli 

 muscles. Seepage 135. 



For the costal portion of the superior intercostal, see 

 page 346. 



The Posterior Scapular. The Third Portion of the Sub- 

 clavian. Figs. 17, 1 8. 



The posterior scapular artery usually arises from this 

 portion of the subclavian. When arising as a branch of the 

 subclavian the posterior scapular takes a course backward 



