PRACTICAL CONSIDERATIONS: AXILLARY ARTERY. 769 



the anterior surface of the subscapularis muscle. External to it is the outer cord of the 

 brachial plexus, and internally the inner cord, which separates it from the axillary vein. 

 In its third portion the artery is covered in its upper half by the lower part of 

 the pectoralis major, but in its lower half only by the integument and the superficial 

 and deep fasciae. The inner head of the median nerve passes obliquely across its 

 anterior surface. Posteriorly it is in relation with the subscapularis, latissimus dorsi, 

 and teres major, in that order from above downward, a considerable amount of areolar 

 tissue, in which run the circumflex and musculo-spiral nerves, intervening, however, 

 between the artery and the muscles. To the outer side are the median and musculo- 

 cutaneous nerves and the coraco-brachialis muscle, while internally are the internal 

 cutaneous and ulnar nerves and the axillary vein. 



Branches. — Much variation occurs in the arrangement of the branches of the 

 axillary artery. It is customary to recognize seven branches, but one or more of 

 them is frequently absent as a distinct branch arising directly from the artery. 

 These branches are arranged as follows : from the first part are given off (i) the 

 superior thoracic and (2) the acromial thoracic ; from the second part (3) the long 

 thoracic and (4) the alar thoracic ; and from the third part (5) the subscapular. 

 (6) the anterior circumjlex, and (7) th.e posterior circumflex. 



Variations. — As stated in the description of the variations of the subclavian, the axillary 

 artery may be represented by two parallel vessels which arise from the first portion of the sub- 

 clavian and are continued below into the radial and ulnar arteries. The more frequent varia- 

 tions, however, concern the occurrence of additional branches from the axillary, and of these 

 there may be mentioned the occurrence of the superior profunda, normally a branch of the 

 brachial, but not infrequently arising from the axillary in common with the subscapular. 



Practical Considerations. — The axillary artery may require to be ligated on 

 account of wounds, of rupture, of high aneurism of the brachial, or, rarely, in distal 

 ligation for subclavian aneurism. 



Wounds of the axillary are not uncommon when the vulnerating body — a knife- 

 blade, a bullet, etc. — is directed from within outward, the artery in all positions of 

 the arm maintaining a much closer relation to the outer, or humeral, wall of the 

 axilla than to the inner, or thoracic, wall, which is therefore known as the wall of 

 safety. It is always well in such cases to expose the artery and to tie both ends, as 

 the exact source of the bleeding is often necessarily in doubt and the free anastomosis 

 of its branches is likely to lead to secondary hemorrhage from the wound if the vessel 

 is tied in continuity. 



Rupture of the axillary artery has occurred in a considerable number of cases as 

 an accident due to the movements employed in attempted reduction of old dislocations 

 of the shoulder. The preponderance of arterial as compared with venous rupture 

 (twenty-six out of twenty-eight cases, Stimson ; or forty out of forty-four, Korte) 

 is striking, the greater thinness of the vein and its attachment to the costo-coracoid 

 membrane — circumstances that would seem to favor its rupture — being more than 

 counterbalanced by the greater frequency and extent of atheromatous degeneration 

 and consequent loss of elasticity in the artery, and possibly by the greater liability 

 of the latter to undergo tension during the movements of abduction, elevation, and 

 circumduction (which are those chiefly associated with the accident in question), and 

 — as the outermost or rather uppermost vessel — to contract adhesion to the displaced 

 humeral head. 



Aneurism of the axillary is comparati\'ely frequent, as might be expected from 

 the number, variety, and range of the movements of the shoulder-joint, during which 

 the vessel is subjected to strains and to a variety of flexures. It is more common on 

 the right side on account of the more general use of the right arm, and affects oftenest 

 the third portion of the vessel, or that least supported by surrounding structures and 

 most subjected to changes in tension and position and to certain injuries, as those 

 which occur during luxation of the shoulder or during efforts at reduction {vide 

 supra'). On account of the looseness of the tissue in which it lies, such an aneurism 

 rapidly attains a large size and, by reason of the minor traumatisms inflicted during 

 the shoulder movements, is especially prone to inflammation. 



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