586 ANGIOLOGY 



On the medial side are the first four ribs with their corresponding Intercostales, 

 and part of the Serratus anterior. On the lateral side, where the anterior and 

 posterior walls converge, the space is narrow, and bounded by the humerus, the 

 Coracobrachialis, and the Biceps brachii. 



Contents. It contains the axillary vessels, and the brachial plexus of nerves, 

 with their branches, some branches of the intercostal nerves, and a large number 

 of lymph glands, together with a quantity of fat and loose areolar tissue. The 

 axillary artery and vein, with the brachial plexus of nerves, extend obliquely along 

 the lateral boundary of the axilla, from its apex to its base, and are placed much 

 nearer to the anterior than to the posterior wall, the vein lying to the thoracic side 

 of the artery and partially concealing it. At the forepart of the axilla, in contact 

 with the Pectorales, are the thoracic branches of the axillary artery, and along 

 the lower margin of the Pectoralis minor the lateral thoracic artery extends to the 

 side of the chest. At the back part, in contact with the lower margin of the Sub- 

 scapularis, are the subscapular vessels and nerves; winding around the lateral 

 border of this muscle are the scapular circumflex vessels; and, close to the neck 

 of the humerus, the posterior humeral circumflex vessels and the axillary nerve 

 curve backward to the shoulder. Along the medial 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 highest thoracic artery. There are some important nerves, 

 however, in this situation, viz., the long thoracic nerve, descending on the surface 

 of the Serratus anterior, to which it is distributed; and the intercostobrachial 

 nerve, perforating the upper and anterior part of this wall, and passing across the 

 axilla to the medial side of the arm. 



The position and arrangement of the lymph glands are described on pages 699 

 and 700. 



The Axillary Artery (A. Axillaris) (Fig. 523). 



The axillary artery, the continuation of the subclavian, commences at the outer 

 border of the first rib, and ends at the lower border of the tendon of the Teres 

 major, where it takes the name of brachial. Its direction varies with the position 

 of the limb; thus the vessel is nearly straight w r hen the arm is directed at right 

 angles with the trunk, concave upward when the arm is elevated above this, and 

 convex upward and lateral ward when the arm lies by the side. At its origin the 

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

 only by the skin and fascia. To facilitate the description of the vessel it is divided 

 into three portions; the first part lies above, the second behind, and the third 

 below the Pectoralis minor. 



Relations. The first portion of the axillary artery is covered anteriorly by the clavicular 

 portion of the Pectoralis major and the coracoclavicular fascia, and is crossed by the lateral 

 anterior thoracic nerve, arjd the thoracoacromial and cephalic veins; posterior to it are the first 

 intercostal space, the corresponding Intercostalis externus, the first and second digitations of 

 the Serratus anterior, and the long thoracic and medial anterior thoracic nerves, and the medial 

 cord of the brachial plexus; on its lateral side is the brachial plexus, from which it is separated 

 by a little areolar tissue; on its medial, or thoracic side, is the axillary vein which overlaps the 

 artery. It is enclosed, together with the axillary vein and the brachial plexus, in a fibrous sheath 

 the axillary sheath continuous above with the deep cervical fascia. 



The second portion of the axillary artery is covered, anteriorly, by the Pectorales major and 

 minor; posterior to it are the posterior cord of the brachial plexus, and some areolar tissue which, 

 intervenes between it and the Subscapularis; on the medial side is the axillary vein, separated 

 from the artery by the medial cord of the brachial plexus and the medial anterior thoracic nerve; 

 on the lateral side is the lateral cord of the brachial plexus. The brachial plexus thus surrounds 

 the artery on three sides, and separates it from direct contact with the vein and adjacent muscles. 



The third portion of the axillary artery extends from the lower border of the Pectoralis minor 

 to the lower border of the tendon of the Teres major. In front, it is covered by the lower part 

 of the Pectoralis major above, but only by the integument and fascia below; behind, it is in rela- 

 tion with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi and Teres 





