566 



THE BLOOD-VASCULAR SYSTEM 



(magnus) in front and the levator scapulae and rhomboideus minor and major behind, to the 

 inferior angle, where it anastomoses with the subscapular artery. It gives off the following 

 branches:— (o) Supraspinous, which ramifies between the supraspinous muscle and the trapezius, 

 and sends branches through the muscle into the fossa, to anastomose with the transverse 

 scapular artery. (6) Infraspinous branches, one or more of which enter the infraspinous 

 fossa, and anastomose with the circumflex (dorsal) scapular, (c) Subscapular branches, which 

 enter the subscapular fossa, and anstomose with the branches of the transverse scapular and 

 subscapular arteries, (d) Muscular branches, to the muscles between which it runs and to 

 the latissimus dorsi. These branches anastomose with the posterior divisions of the intercostal 

 arteries. 



(2) The ascending branch or superficial cervical artery [r. ascendens], smaller than the 

 descending branch, ascends under the anterior margin of the trapezius, lying upon the levator 

 scapulae and splenius muscles. It supphes branches to the trapezius, levator scapulae, and 

 splenius muscles, and the posterior chain of lymphatic glands. It anastomoses with the 

 superficial branch of the descending branch of the occipital between the splenius and semi- 

 spinahs capitis (complexus). It is accompanied by two veins. This artery may arise directly 

 from the thyreoid axis, or from the third part of the subclavian artery. 



3. THE INTERNAL MAMMARY ARTERY 



The internal mammary artery [a. mammaria interna] (figs. 457, 462) comes off 

 from the lower part of the first portion of the subclavian, usually opposite the 



Fig. 462. — Scheme of the Right Internal Mammary Artery. (Walsham.) 



, Common carotid artery 



Phrenic nerve ^ 

 Subclavian artery 

 Subclavian vein, cut 



Anterior intercostal branch 



Anterior intercostal branch 



Muscalo-phrenic artery 



Deep circumflex iliac artery 



Internal jugular vein 

 Subclavian vein, cut 

 Scalenus anterior muscle 



Sternum 



Transversus thoracis muscle 

 Perforating branch 



Superior epigastric artery 



■Inferior epigastric artery 



thyrco-cervical trunk (thyreoid axis), close to the medial edge of the scalenus 

 anterior, occasionally opposite the vertebral, or at a spot between these two ves- 

 sels. It descends with a slight inclination forward and mcdialward, under cover 

 of the clavicle, and enters the thorax l^eiiind the cartilage of the first rib, and 

 thence passes down behind the cartilages of the next succeeding ribs, about 1.2 cni. 

 (^ in. ) from the lateral margin of the sternum, to the sixth interspace, where it 

 divides into the superior epigastric and musculo-phrenic. It is accompanied by 

 two veins, which unite into one trunk behind the first intercostal muscle; this 



