196 PRACTICAL ANATOMY. 



The Axillary Artery and Vein. -This artery has three stages, as follows : 



1. First stage, from first rib to the pectoralis minor muscle. 



2. Second stage, behind the pectoralis minor muscle. 



3. Third stage, below the pectoralis minor muscle. 



Note that the axillary vein lies internal to the artery in all three stages ; 

 that it receives two large tributaries : (i) the cephalic, (2) the basilic veins. 



Jiranclies of the axillarv artcrv according to stages : 



First Stage. (i) The superior tlioracic passes between the pectoral muscles 

 to the chest walls. Trace branches from it to these muscles and to the thoracic 

 walls. (2) The acrotnio-thoracic perforates the clavi-pectoral fascia (Fig. 132), 

 and sends branches to the deltoid and pectoral muscles. Its descending branch 

 you found deeply buried in a groove with the cephalic vein, between the deltoid 

 and pectoralis major muscles. 



Second Stage. (i) Alar tlioracic branches have been seen supplying the 

 axillary glands and fat. (2) The long tlioracic you will find in the anterior thoracic 

 angle. Trace its numerous branches to all the walls of the axillary space. 



Third Stage. (i) The anterior circumflex artery you will trace behind the 

 coraco-brachial and biceps muscles. It sends a branch to the shoulder-joint 

 through the bicipital groove. (2) The posterior cironnjlex passes through the 

 quadrangular space, with the circumflex nerve, to the deltoid muscle and 

 shoulder-joint. The space referred to is bounded externally by the humerus, 

 internally by the scapular head of the triceps, superiorly by the teres minor, 

 inferiorly by the teres major and latissiinus dorsi. (3) The subscapnlar is the 

 largest branch of the axillary artery. You will find it in the posterior thoracic 

 angle. It passes through the triangular space, and takes the name of dorsalis 

 scapulce. This space is bounded by the triceps and the teres minor and major. 



The muscles in this locality are : 



1. The Serratus Magnus. This arises from the outer surface of the upper 

 eight ribs by nine fleshy processes. (Fig. 135.) It is inserted into the anterior 

 lip of the vertebral border of the scapula. It is supplied by the long thoracic 

 nerve, a branch of the brachial plexus. (Fig. 42.) 



2. The Subscapularis Muscle. This arises from the subscapular fossa and 

 is inserted into the lesser tuberosity of the humerus. 



3. The teres major arises from the middle lip of the axillary border of the 

 scapula. It is inserted into the posterior lip of the bicipital groove of the 

 humerus with its synergist, the latissimus dorsi. 



4. The latissimus dorsi is a muscle of the back, and will be described in the 

 proper place. The student will now trace the subscapular nerves, from the pos- 

 terior cord of the brachial plexus to the subscapular, the teres major, and the 

 latissimus dorsi muscles. Also study the relation and manner of insertion of the 

 two latter muscles into the humerus. 



The Brachial Artery. This vessel begins as a continuation of the axillary 

 artery, at the lower border of the teres major muscle. (Fig. 137.) It ends at 

 the elbow, by dividing into the radial and ulnar arteries. In its course you can 

 show the triceps muscle on one side and the biceps and coraco-brachial on the 

 other side of this artery. The median basilic vein lies in front of it, near the elbow 

 (Fig. 105), the bicipital fascia intervening. The median nerve crosses it in the 

 middle of its course. As you must demonstrate on your work, this artery lies 

 superficially in its entire course, and may be easily reached for compression or 

 operation. Find the ulnar and internal cutaneous nerves, internal to the artery. 

 Examine every cadaver in the room to find high bifurcations of the brachial 

 artery. 



The branches of the brachial artery are : 



I. The muscular brandies to the flexor muscles of the forearm. 



