THE AXILLARY ARTERY. 531 



internal cutaneous nerve, and behind, the musculo-spiral and circumflex, the latter 

 extending only to the lower border of the Subscapularis muscle. 



RELATIONS OF THE THIRD PORTION OF THE AXILLARY ARTERY. 



In front. 



Integument and fascia. 

 Pectoral!? major. 

 Inner head of median nerve. 

 Internal cutaneous nerve. 



Outer side. f \ Inner side. 



Coraco-brachialis. ( ^tl^ | Ulnar nerve. 



Median nerve. I Third portion. J Axillary vein. 



Musculo-cutaneous nerve. \ / Lesser internal cutaneous nerve. 



Behind. 



Subscapularis. 



Tendons of Latissimus dorsi and Teres major. 



Musculo-spiral and circumflex nerves. 



Peculiarities. The axillary artery, in about one case out of every ten, gives off a large 

 branch, which forms either one of the arteries of the forearm or a large muscular trunk. In the 

 first set of cases this artery is most frequently the radial (1 in 33), sometimes the ulnar (1 in 72), 

 and, very rarely, the interosseous (1 in 506). In the second set of cases the trunk has been 

 found to give origin to the subscapular. circumflex, and profunda arteries of the arm. Some- 

 times only one of the circumflex, or one of the profunda arteries, arose from the trunk. In 

 these cases the brachial plexus surrounded the trunk of the branches and not the main vessel. 



Surface Marking. The course of the axillary artery may be marked out by raising the 

 arm to a right angle and drawing a line from the middle of the clavicle to the point where the 

 tendon of the Pectoralis major crosses the prominence caused by the Coraco-brachialis as it 

 emerges from under cover of the anterior fold of the axilla. The third portion of the artery can 

 be felt pulsating beneath the skin and fascia, at the junction of the anterior with the middle 

 third of the space between the anterior and posterior folds of the axilla, close to the inner border 

 of the Coraco-brachialis. 



Surgical Anatomy. The student, having carefully examined the relations of the axillary 

 artery in its various parts, should now consider in what situation compression of this vessel 

 may be most easily effected, and the best position for the application of a ligature to it when 

 necessary. 



Compression of the vessel may be required in the removal of tumors or in amputation of 

 the upper part of the arm ; and the only situation in which this can be effectually made is in the 

 lower part of its course ; by pressing on it in this situation from within outward against the 

 humerus the circulation may be effectually arrested. 



The axillary artery is perhaps more frequently lacerated than any other artery in the body, 

 with the exception of the popliteal, by violent movements of the upper extremity, especially in 

 those cases where its coats are diseased. It has occasionally been ruptured in attempts to reduce 

 old dislocations of the shoulder-joint. This lesion is most likely to occur during the preliminary 

 breaking down of adhesions, in consequence of the artery having become fixed to the capsule 

 of the joint. Aneurism of the axillary artery is ot frequent occurrence, a large percentage of 

 the cases being traumatic in their origin, due to the violence to which it is exposed in the varied, 

 extensive, and often violent movement of the limb. 



The application of a ligature to the axillary artery may be required in cases of 

 aneurism of the upper part of the brachial or as a distal operation for aneurism of the sub- 

 clavian ; and there are only two situations in which it can be secured viz. in the first and in the 

 third parts of its course ; for the axillary artery at its central part is so deeply seated, and, at the 

 same time, so closely surrounded with large nervous trunks, that the application of a ligature to 

 it in that situation would be almost impracticable. 



In the third part of its course the operation is most simple, and may be performed in the 

 following manner: The patient being placed on a bed and the arm separated from the side, with 

 the hand supinated, an incision is made through the integument forming the floor of the axilla 

 about two inches in length, a little nearer to the anterior than the posterior fold of the axilla. 

 After carefully dissecting through the areolar tissue and fascia, the median nerve and axillary 

 vein are exposed ; the former having been displaced to the outer and the latter to the inner side 

 of the arm, the elbow being at the same time bent, so as to relax the structures and facilitate 

 their separation, the ligature may be passed round the artery from the ulnar to the radial side. 



This portion of the artery is occasionally crossed by a muscular slip, the axillary arch, derived 

 from the Latissimus doifci, which may mislead the surgeon during an operation. The occasional 

 existence of this muscular fasciculus was sp9ken of in the description of the muscles, 

 easily be recognized by the transverse direction of its fibres. 



