INTERNAL MAMMARY ARTERY. 299 



muscles on the dorsum of the scapula, and inosculates with the posterior 

 scapular, and beneath the acromion process with the dorsal branch of the 

 subscapular artery. At the supra-scapular notch it sends a large branch to 

 the trapezius muscle. The supra-scapular artery is not unfrequently a 

 branch of the subclavian. 



The POSTERIOR SCAPULAR ARTERY (transversalis colli) passes trans- 

 versely across the subclavian triangle at the root of the neck, to the supe- 

 rior angle of the scapula. It then descends along the posterior border of 

 that bone to its inferior angle, where it inosculates with the subscapular 

 artery, a branch of the axillary. In its course across the neck it passes in 

 front of the scalenus anticus, and across the brachial plexus ; in the rest 

 of its course it is covered in by the trapezius, levator anguli scapulae, 

 rhomboideus minor, and rhomboideus major muscles. Sometimes it passes 

 behind the scalenus anticus, and between the nerves, which constitute the 

 brachial plexus. This artery, which is very irregular in its origin, pro- 

 ceeds more frequently from the third portion of the subclavian artery than 

 from the first. 



The posterior scapular gives branches to the neck, and opposite the 

 angle of the scapula inosculates with the profunda cervicis. It supplies 

 the muscles along the posterior border of the scapula, and establishes an 

 important anastomotic communication between the branches of the exter- 

 nal carotid, subclavian, and axillary arteries. 



The SUPERFICIALIS CERVICIS ARTERY (cervicalis anterior) is a small 

 vessel, which ascends upon the anterior tubercles of the transverse pro- 

 cesses of the cervical vertebrae, lying in the groove between the scalenus 

 anticus and rectus anticus major. It is distributed to the deep muscles 

 and glands of the neck, and sends branches through the intervertebral 

 foramina to supply the spinal cord and its membranes. 



The PROFUNDA CERVICIS (cervicalis posterior) passes backwards between 

 the transverse processes of the seventh cervical and first dorsal vertebraa, 

 and then ascends the back part of the neck, between the complexus and 

 semi-spinalis colli muscles. It inosculates above with the princeps cervicis 

 of the occipital artery, and below, by a descending branch, with the pos- 

 terior scapular. 



The SUPERIOR INTERCOSTAL ARTERY descends behind the pleura upon 

 the necks of the first two ribs, and inosculates with the first aortic inter- 

 costal. It gives off two branches \vhich supply the first two intercostal 

 spaces. 



The INTERNAL MAMMARY ARTERY descends by the side of the sternum, 

 resting against the costal cartilages, to the diaphragm ; it then pierces the 

 anterior fibres of the diaphragm, and enters the sheath of the rectus, where 

 it inosculates with the epigastric artery, a branch of the external iliac. In 

 the upper part of its course it is crossed by the phrenic nerve, and lower 

 down lies between the triangularis sterni and the internal intercos+aj 

 muscles. 



The Branches of the internal mammary are, 



Anterior intercostal, Mediastinal, 



Mammary, Pericardiac, 



Comes neivi phrenici, Musculo-phrenic. 



