



THE AXILLA 585 



The Superior Epigastric Artery (a. epigastrica superior} continues in the original 

 direction of the internal mammary; it descends through the interval between the 

 costal and sternal attachments of the diaphragm, and enters the sheath of the 

 Rectus abdominis, at first lying behind the muscle, and then perforating and sup- 

 plying it, and anastomosing with the inferior epigastric artery from the external 

 iliac. Branches perforate the anterior wall of the sheath of the Rectus, and supply 

 the muscles of the abdomen and the integument, and a small branch passes in 

 front of the xiphoid process and anastomoses with the artery of the opposite side. 

 It also gives some twigs to the diaphragm, while from the artery of the right 

 side small branches extend into the falciform ligament of the liver and anastomose 

 with the hepatic artery. 



4. The costocervical trunk (truncus costocervicalis; superior intercostal arlery) 

 (Fig. 513) arises from the upper and back part of the subclavian artery, behind 

 the Scalenus anterior on the right side, and medial to that muscle on the left side. 

 Passing backward, it gives off the profunda cervicalis, and, continuing as the highest 

 intercostal artery, descends behind the pleura in front of the necks of the first and 

 second ribs, and anastomoses with the first aortic intercostal. As it crosses the 

 neck of the first rib it lies medial to the anterior division of the first thoracic nerve, 

 and lateral to the first thoracic ganglion of the sympathetic trunk. 



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 for the 

 second intercostal space usually joins with one from the highest aortic intercostal 

 artery. This branch is not constant, but is more commonly found on the right 

 side; when absent, its place is supplied by an intercostal branch from the aorta. 

 Each intercostal gives off a posterior branch which goes to the posterior vertebral 

 muscles, and sends a small spinal branch through the corresponding intervertebral 

 foramen to the medulla spinalis and its membranes. 



The Profunda Cervicalis (a. cervicalis profunda; deep cervical branch) arises, in 

 most cases, from the costocervical trunk, and is analogous to the posterior branch 

 of an aortic intercostal artery: occasionally it is a separate branch from the sub- 

 clavian artery. Passing backward, above the eighth cervical nerve and between 

 the transverse process of the seventh cervical vertebra and the neck of the first rib, 

 it runs up the back of the neck, between the Semispinales capitis and colli, as high 

 as the axis vertebra, supplying these and adjacent muscles, and anastomosing with 

 the deep division of the descending branch of the occipital, and with branches of 

 the vertebral. It gives off a spinal twig which enters the canal through the inter- 

 vertebral foramen between the seventh cervical and first thoracic vertebrae. 



THE AXILLA. 



The axilla is a pyramidal space, situated between the upper lateral part of the 

 chest and the medial side of the arm. 



Boundaries. The apex, which is directed upward toward the root of the neck, 

 corresponds to the interval between the outer border of the first rib, the superior 

 border of the scapula, and the posterior surface of the clavicle, and through it 

 the axillary vessels and nerves pass. The base, directed downward, is broad at 

 the chest but narrow and pointed at the arm; it is formed by the integument and a 

 thick layer of fascia, the axillary fascia, extending between the lower border of the 

 Pectoralis major in front, and the lower border of the Latissimus dorsi behind. 

 The anterior wall is formed by the Pectorales major and minor, the former covering 

 the whole of this wall, the latter only its central part. The space between the upper 

 border of the Pectoralis minor and the clavicle is occupied by the coracoclavicular 

 fascia. The posterior wall, which extends somewhat lower than the anterior, is 

 formed by the Subscapularis above, the Teres major and Latissimus dorsi below. 





