402 ARTERIES. 



TJieir Position. The axillary artery and vein, with the brachial plexus of nerves, 

 extend obliquely along the outer boundary of the axillary space, from its apex to 

 its base, and are placed much nearer the anterior than the posterior wall, the vein 

 lying to the inner or thoracic side of the artery, and altogether concealing it. 

 At the fore part of the axillary space, in contact with the Pectoral 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 sub- 

 scapular vessels and nerves ; winding around the lower border of this muscle, are 

 the dorsalis scapulae artery and veins ; and towards the outer extremity of the 

 muscle, the posterior circumflex vessels and nerve are seen curving backwards to 

 the shoulder. 



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

 part being crossed by a few small branches from the superior thoracic artery. 

 There are some important nerves, however, in this situation ; 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, are the intercosto-humeral nerves, which pass 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 inconsiderable 

 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 nerves 

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

 geon 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 most fortunate circumstance, for it 

 is in this situation more especially that tumors requiring removal are most fre- 

 quently 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, when it becomes the 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 out- 

 wards ; when it is directed at right angles with the trunk, the vessel is nearly 

 straight ; and if elevated still higher, it 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 may be facilitated by its division 

 into three portions ; the first portion being that above the Pectoralis minor, the 

 second portion beneath, and the third, below, that muscle. 



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

 portion of the Pectoralis major, the costo-coracoid membrane, and the cephalic 

 vein ; behind, with the first intercostal space, the corresponding 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. 



