400 ARTERIES. 



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 brandies 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 these 

 muscles. They supply the Intercostal and Pectoral muscles, and the mammary 

 gland. 



The anterior or perforating arteries correspond to the five or six upper inter- 

 costal spaces. They arise from the internal mammary, pass forwards through the 

 intercostal spaces, and, curving outwards, supply the Pectoral is major, and the 

 integument. Those which correspond to the first three spaces are distributed to 

 the mammary 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 iii size, opposite the last intercostal 

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

 across which it passes ; they diminish in size as the spaces decrease in length, and 

 are distributed in a manner precisely similar to the anterior intercostals from the 

 internal mammary. It also gives branches backwards to the Diaphragm, and 

 downwards to the abdominal muscles. 



The superior epigastric continues in the original direction of the internal mam- 

 mary, descends behind the Eectus muscle, and, perforating its sheath, divides into 

 branches which supply the Rectus, anastomosing with the epigastric 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, anastomoses in front of that 

 cartilage with the artery of the opposite side. 



The SUPERIOR INTERCOSTAL arises from the upper and back part of the sub- 

 clavian artery, beneath 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 similar manner with the aortic 

 intercostals. The branch for the second intercostal space usually joins with one 

 from the first aortic intercostal. Each intercostal gives off a branch to the posterior 

 spinal muscles, and a small one, which passes through the corresponding inter- 

 vertebral 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 intercostal artery. 

 Passing backwards, between the transverse process of the seventh cervical vertebra 

 and the first rib, it ascends the back part of the neck, between the Complexus 

 and Semi-spinalis 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. 



