AXILLARY ARTERY. 



363 



In almost every disease in the axilla the arm 

 swells on account of the pressure exerted on 

 the absorbents and veins. 



For the BIBLIOGRAPHY see that of ANATOMY 

 (INTRODUCTION). 



(Charles Benson.) 



AXILLARY ARTERY (arteria axillaris). 

 This artery, which is the continuation of the 

 subclavian trunk, commences at the outer 

 border of the first rib, beneath the lower mar- 

 gin of the subclavius muscle : lying at first on 

 the external surface of the superior part of the 

 thorax, it traverses the axillary space, applies 

 itself to the internal side of the upper extre- 

 mity, and terminates at the lower edge of the 

 tendon of the teres major muscle. The ave- 

 rage length of this vessel is about six inches : 

 when the arm hangs by the side it describes a 

 curve in its course, the concavity of which is 

 downwards and inwards, but it is brought to a 

 nearly horizontal right line by raising the arm 

 to a right angle with the trunk, and it may be 

 made to describe a curve, the concavity of 

 which is turned upwards, by raising the arm to 

 the greatest possible extent of elevation. 



The depth of this artery from the surface is 

 greatest at its commencement, whence to its 

 termination it gradually becomes more superfi- 

 cial. 



Relations. Anteriorly the axillary artery is 

 covered by the following parts ; on first emer- 

 ging from under the margin of the subclavius 

 muscle, it is covered by the costo-coracoid li- 

 gament, beneath which the anterior thoracic 

 nerves coming from the brachial plexus cross 

 it in their course to the pectoral muscles, the 

 vessel then passes under the pectoralis minor 

 muscle, from the lower edge of which to its 

 termination the coraco-brachialis lies in front 

 of it. Posteriorly it rests at its commence- 

 ment on the first intercostal muscle, then, 

 with the interposition of a considerable quan- 

 tity of cellular tissue, on the first digitation 

 of the serratus magnus, which separates it 

 from the external surface of the second rib, 

 it next crosses the tendon of the subsca- 

 pularis muscle, from the lower edge of which 

 to its termination it lies on the anterior sur- 

 face of the tendon of the teres major. Ex- 

 ternally it is bounded by the lowest cord of 

 the brachial plexus, until it arrives at the supe- 

 rior edge of the subscapularis, and for the re- 

 maining part of its course by the commence- 

 ment, of thf external cutaneous nerve. Inter- 

 nally it is bounded by the axillary vein, which 

 is in contact with it in the whole of its course, 

 except while crossing the subscapularis, where 

 the internal root of the median and the ulnar 

 nerve separate the vein from the artery. 



The lesser pectoral muscle, in crossing the 

 axilla at the lower part of the upper third of 

 that region, divides the axillary artery into three 

 stages. The first extends from the clavicle to 

 the upper edge of the lesser pectoral ; in this 

 stage the most important relation which the 

 artery has, is to the vein, which lies upon its 

 inner side and upon a plane anterior to it, so 

 that in a state of distension the vein would 



overlap the artery. All the nerves are behind 

 and external to it. In the second stage, which 

 is that concealed by the lesser pectoral, the 

 vein, still on the thoracic side and more an- 

 terior, is separated from the artery by the 

 nerves, which, forming the axillary plexus, are so 

 closely applied to it, behind and on each side, 

 as to form, as Velpeau remarks, a complete 

 nervous sheath. In the third stage, which is 

 below the lesser pectoral and in immediate 

 connexion with the subscapularis muscle, the 

 artery is still in the midst of nerves, having on 

 each side a root of the median, together with 

 the external cutaneous nerve on the outside 

 and the internal cutaneous and ulnar on the 

 inside, the circumflex and musculo-spiral being 

 posterior to it. In this stage the vein is in- 

 ternal and superficial to the artery, but sepa- 

 rated from it by the nerves which lie on its 

 internal side. 



A ligature cannot be placed on the axillary 

 artery in any stage of its course without endan- 

 gering parts of great importance ; in the second 

 stage, however, the connexion of the artery 

 with the axillary plexus is so intimate as com- 

 pletely to preclude the possibility of tying it 

 there without incurring the greatest risk of 

 serious injury. Hence there are but two situ- 

 ations in which it can be deemed prudent to 

 expose this artery. Of these the operation in 

 the third stage may be accomplished with 

 greater facility, because the artery is here much 

 more superficial, and although its relations are 

 numerous, and in some degree complicated, 

 they admit of being separated from the artery 

 to such a. distance as will guard them from 

 injury. To tie the artery in the first stage, 

 however, is much more difficult, chiefly in 

 consequence of the great depth at which it 

 lies, the necessity there is for cutting through 

 large muscles, and the almost certainty of 

 troublesome and unavoidable venous hemor- 

 rhage. The principal part which the surgeon 

 has to avoid in applying the ligature needle is 

 the vein. 



'Branches. The axillary artery usually gives 

 off six branches, viz.; 1. theacromial; 2. the 

 superior thoracic ; 3. the inferior or long tho- 

 racic or external mammary; 4. the subscapu- 

 lar ; 5. the posterior circumflex ; 6. the ante- 

 rior circumflex. 



] . The acromial artery (thoracica acromia- 

 lis) arises from the anterior side of the axillary 

 artery above the edge of the lesser pectoral 

 muscle, and after having given off some 

 branches to the subclavius, serratus magnus, 

 and first intercostal, it passes obliquely down- 

 wards and outwards, piercing the expansion of 

 the costo-coracoid ligament, and arrives at the 

 posterior surface of the deltoid muscle, where 

 it divides into a superior and an inferior 

 branch. 



The superior branch mounts by a tortuous 

 course towards the clavicle ; this branch, which 

 is more particularly designated by the term 

 acromial, after having given off one or more 

 branches to the deltoid muscle and the integu- 

 ments, runs along the anterior border of the 

 clavicle, behind the origin of the deltoid, until 



