SURGICAL ANATOMY OF THE AXILLA. 527 



Those which correspond to the second, third, and fourth spaces ai-e distributed to 

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



The musculo-phrenic artery is directed obliquely downward and outward, 

 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 Rectus 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 

 vessels 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. 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. 



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. 289) arises from the upper and back part of the 

 subclavian artery, behind the Anterior scalenus muscle on the right side, and to 

 the inner side of that 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. As it crosses the 

 neck of the first rib it lies to the inner side of the anterior division of the first 

 dorsal nerve and to the outer side of the first thoracic ganglion of the sympathetic. 

 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. Each 

 intercostal gives off a branch to 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 ; occasionally it arises as a separate branch from the subclavian artery. 

 Passing backward, above the eighth cervical nerve and 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 Avith the deep branch 

 of the arteria princeps cervicis of the occipital, and with branches which pass out- 

 ward from the vertebral. It gives off a special branch which enters the spinal 

 canal through the intervertebral foramen between the seventh cervical and first 

 dorsal vertebrae. 



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 apex, which is directed upward toward the root of the neck, 

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



