AXILLARY. 479 



toral muscles, are the thoracic branches of the axillary artery, and along the 

 anterior margin of the axilla the long thoracic artery extends to the side of the 

 chest. At the back part, in contact with the lower margin of the Subscapularis 

 muscle, are the subscapular vessels and nerves; winding around the lower 

 border of this muscle, is the dorsalis scapula? artery and veins; and towards the 

 outer extremity of the muscle, the posterior circumflex vessels and the circum- 

 flex nerve are seen curving backwards to the shoulder. 



Along the inner or thoracic side no vessel of any importance exists, the upper 

 part of the space being crossed merely by a few small branches from the supe- 

 rior thoracic artery. There are some important nerves, however, in this situa- 

 tion, viz., the posterior thoracic or external respiratory nerve, descending on 

 the surface of the Serratus Magnus, to which it is distributed; and perforating 

 the upper and anterior part of this wall, the intercosto-humeral nerve or nerves, 

 passing across the axilla to the inner side of the arm. 



The cavity of the axilla is filled by a quantity of loose areolar tissue, a large 

 number of small arteries and veins, all of which are, however, of inconsider- 

 able size, and numerous lymphatic glands ; these are from ten to twelve in 

 number, and -situated chiefly on the thoracic side, and lower and back part of 

 this space. 



The student should attentively consider the relation of the vessels and nerver 

 in the several parts of the axilla ; for it not unfrequently happens that the 

 surgeon is called upon to extirpate diseased glands, or to remove a tumor from 

 this situation. In performing such an operation, it will be necessary to proceed 

 with much caution in the direction of the outer wall and apex of the space, as 

 here the axillary vessels will be in danger of being wounded. Towards the 

 posterior wall, it will be necessary to avoid the subscapular, dorsalis scapulas, 

 and posterior circumflex vessels, and, along the anterior wall, the thoracic 

 branches. It is only along the inner or thoracic wall, and in the centre of the 

 axillary cavity, that there are no vessels of any importance ; a fortunate cir- 

 cumstance, for it is in this situation more especially that tumors requiring re- 

 moval are usually situated. 



THE AXILLARY ARTERY. 



The Axillary Artery, the continuation of the subclavian, commences at the 

 lower border of the first rib, and terminates at the lower border of the tendons 

 of the Latissimus Dorsi and Teres Major muscles, where it takes the name of 

 brachial. Its direction varies with the position of the limb ; when the arm lies 

 by the side of the chest, the vessel forms a gentle curve, the convexity being 

 upwards and outwards : when it is directed at right angles with the trunk, the 

 vessel is nearly straight ; and when it is elevated still higher, the artery describes 

 a curve, the concavity of which is directed upwards. At its commencement 

 the artery is very deeply situated, but near its termination is superficial, being 

 covered only by the skin and fascia. The description of the relations of this 

 vessel is facilitated by its division into three portions, the first portion being 

 that above the Pectoralis Minor ; the second portion, behind ; and the third, 

 below that muscle. 



The first portion of the axillary artery is in relation, in front, with the clavi- 

 cular portion of the Pectoralis Major, the costo-coracoid membrane, the Sub- 

 clavius, and the cephalic vein ; behind, with the first intercostal space, the corre- 

 sponding Intercostal muscle, the first serration of the Serratus Magnus, and the 

 posterior thoracic nerve ; on its outer side with the brachial plexus, from which 

 it is separated by a little cellular interval ; on its inner, or thoracic side, with 

 the axillary vein. 



