188 HUMAN ANATOMY. 



supra-acromial branch to the skin over the acromion, anastomos- 

 ing with the posterior circumflex and acromial thoracic arteries. 



In about 50 per cent, of bodies this artery will be found to arise 

 from the third portion of the subclavian. 



5. The transver satis colli passes outward to the trapezius 

 muscle, where it divides into 



The (a) superficial cervical, an important branch passing beneath 

 the trapezius to anastomose with the superficial branch of the arteria 

 princeps cervicis; 



And the (b) posterior scapular, the larger passing to and along 

 the upper and posterior border of the scapula, beneath the levator 

 anguli scapulae, rhomboidei, latissimus dorsi and trapezius, to anas- 

 tomose with the subscapular, suprascapular, and posterior branches of 

 the intercostals. 



6. The internal mammary arises from the subclavian, oppo- 

 site the thyroid axis, and descends upon the internal surfaces 

 of the costal cartilages to between the sixth intercostal space, 

 where it divides into the musculo-phrenic and the superior epi- 

 gastric. Its branches are : 



Comes nervi phrenici (superior phrenic), supplies diaphragm, pass- 

 ing between the pleura and pericardium; 



Mediastinal, to the anterior mediastinum; 



Pericardiac, to upper portion of pericardium; 



Sternal, to posterior surface of sternum; 



Anterior intercostal, to fifth or sixth upper intercostal spaces; 



Perforating, perforate the intercostal spaces to supply the mam- 

 mary gland; 



Musculo-phrenic, supplies lower part of pericardium, diaphragm, 

 and upper part of abdominal muscles; 



Superior epigastric, supplies the rectus muscle, and anastomoses 

 with the deep epigastric from the external iliac. 



7. The superior intercostal artery arises from the subclavian, 

 behind the anterior scalenus muscle, and descends behind the 

 pleura and anastomoses with the first aortic intercostal artery. 

 It gives off branches in the intercostal spaces to the spinal cord 

 and its membranes and the posterior spinal muscles. Its princi- 

 pal branch is the deep cervical (profunda cervicis). 



THE AXILLARY ARTERY 



is the continuation of the subclavian, extending outward from 

 the lower edge of the first rib to the lower margin of latissimus 

 dorsi and teres major muscles, where it becomes the brachial. It 

 is divided by the pectoralis minor into three parts the first 

 portion above, the second portion behind, and the third portion 



