si'RGICAL AXATOMY OF THE AXILLA. 



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 inter- 

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

 spaces across which it passes; these 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. The musculo-phrenic also gives branches to the 

 lower part of the pericardium, and others which run backward to the Diaphragm 

 and downward to the abdominal muscles. 



The superior epigastric continues in the original direction of the internal 

 mammary : it descends through the cellular interval between the costal and sternal 

 attachments of the Diaphragm, and enters the sheath of the ftectus abdominis 

 muscle, at first lying behind the muscle, and then perforating it and supplying it, 

 and anastomosing with the deep epigastric artery from the external iliac. Some 

 Is perforate the sheath of the Rectus, and supply the muscles of the abdomen 

 and the integument, and a small branch, which passes inward upon the side of the 

 ensiform appendix, anastomoses in front of that cartilage with the artery of the 

 opposite side. 



Surgical Anatomy. The course of the internal mammary artery may be defined by draw- 

 ing a line across the six upper intercostal spaces half an inch from and parallel with the sternum. 

 The position of the vessel must be remembered, as it is liable to be wounded in stabs of the 

 chest-wall. It is most easily reached by a transverse incision in the second intercostal space. 



The Superior Intercostal (Fig. 352) 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 backward, 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. 1 In the first intercostal 

 space it gives off a branch which is distributed in a manner similar to the distri- 

 bution of the aortic intercostals. The branch for the second intercostal space 

 usually joins with one from the aortic intercostals. Each intercostal gives off a 

 branch to the posterior spinal muscles, and a small one, spinal, 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 backward, 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 deep branch of the arteria 

 princeps cervicis of the occipital and with branches which pass outward from the 

 vertebral. 



SURGICAL ANATOMY OF THE AXILLA. 



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

 the chest and the inner side of the arm. 



Boundaries. Its apei\ which is directed upward toward the root of the neck, 

 corresponds to the interval between the first rib. the upper edge of the scapula, 

 and the clavicle, through which the axillary vessels and nerves pass. The base, 

 directed downward, is formed by the integument, and a thick layer of fascia 

 extending between the lower border of the Pectoralis major in front, and the lower 

 border of the Latissimus dorsi behind ; it is broad internally at the chest, but 

 narrow and pointed externally at the arm. The anterior boundary is formed by 

 the Pectoralis major and minor muscles, the former covering the whole of the 

 anterior wall of the axilla, the latter covering only its central part. The posterior 

 boundary, which extends somewhat lower than the anterior, is formed by the Sub- 

 scapularis above, the Teres major and Latissimus dorsi below. On the inner side 

 are the first four ribs with their corresponding Intercostal muscles, and part of the 

 Serratus magnus. On the outer side, where the anterior and posterior boundaries 



1 See foot-note, p. 607. 



