INTERNAL MAMMARY. 477 



Diaphragm, to which it is distributed; anastomosing with the other phrenic 

 arteries from the internal mammary, and abdominal aorta. 



The mediastinal branches are small vessels, which are distributed to the areolar 

 tissue in the anterior mediastinum, and the remains of the thymus gland. 



The pericardiac branches supply the upper part of the pericardium, the lower 

 part receiving branches from the musculo-phrenic artery. Some sternal branches 

 are distributed to the Triangularis Sterni, and both surfaces of the sternum. 



The anterior intercostal arteries supply the five or six upper intercostal spaces. 

 The branch corresponding to each space passes outwards, and soon divides into 

 two, which run along the opposite borders of the ribs, and inosculate with the 

 intercostal arteries from the aorta. They are at first situated between the 

 pleura and the Internal Intercostal muscles, and then between the two layers 

 of those muscles. They supply the Intercostal and Pectoral muscles, and the 

 mammary gland. 



The perforating arteries correspond to the five or six upper intercostal spaces. 

 They arise from the internal mammary, pass forwards through the intercostal 

 spaces, and curving outwards, supply the Pectoralis Major, and the integument. 

 Those which correspond to the first three spaces, are distributed to the mam- 

 mary gland. In females, during lactation, these branches are of large size. 



The musculo-phrenic artery is directed obliquely downwards and outwards, 

 behind the cartilages of the false ribs, perforating the Diaphragm at the eighth 

 or ninth rib, and terminating, considerably reduced in size, opposite the last 

 intercostal space. It gives off anterior intercostal arteries to each of the inter- 

 costal spaces across which it passes ; these diminish in size as the spaces de- 

 crease in length, and are distributed in a manner precisely similar to the 

 anterior intercostals from the internal mammary. The musculo-phrenic also 

 gives branches backwards to the Diaphragm, and downwards to the abdominal 

 muscles. 



The superior epigastric continues in the original direction of the internal 

 mammary, descends behind the Eectus muscle, and perforating its sheath, 

 divides into branches which supply the Rectus, anastomosing with the epi- 

 gastric artery from the external iliac. Some vessels perforate the sheath of the 

 Rectus, and supply the muscles of the abdomen and the integument, and a small 

 branch which passes inwards upon the side of the ensiform appendix, anasto- 

 moses in front of that cartilage with the artery of the opposite side. 



The Superior Intercostal (Fig. 279) arises from the upper and back part of the 

 subclavian artery, behind the Anterior Scalenus on the right side, and to the 

 inner side of the muscle on the left side. Passing backwards, it gives off the 

 deep cervical branch, and then descends behind the pleura in front of the necks 

 of the first two ribs, and inosculates with the first aortic intercostal. In the 

 first intercostal space, it gives off a branch which is distributed in a manner 

 similar to the distribution of the aortic intercostals. The branch of the second 

 intercostal space usually joins with one from the first aortic intercostal. Each 

 intercostal gives off a branch of the posterior spinal muscles, and a small one, 

 which passes through the corresponding intervertebral foramen to the spinal 

 cord and its membranes. 



The deep cervical branch (profunda cervicis) arises, in most cases, from the 

 superior intercostal, and is analogous to the posterior branch of an aortic inter- 

 costal artery. Passing backwards, between the transverse process of the 

 seventh cervical vertebra and the first rib, it runs up the back part of the neck, 

 between the Complexus and Semispinalis Colli muscles, as high as the axis, 

 supplying these and adjacent muscles, and anastomosing with the arteria 

 princeps cervicis of the occipital, and with branches which pass outwards from 

 the vertebral. 



