AXILLARY. 481 



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. 



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

 tery 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 is 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 outwards against the humerus, 

 the circulation may be effectually suspended. 



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

 the upper part of the brachial; 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, the head of the humerus is felt for, and an incision made through the integu- 

 ment over it, 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 derived from 

 the Latissitnus Dorsi, which may mislead the surgeon during an operation. The occasional 

 existence of this muscular fasciculus was spoken of in the description of the muscles. It may 

 easily be recognized by the transverse direction of its fibres. 



The first portion of the axillary artery may be tied, in cases of aneurism encroaching so far 

 upwards that a ligature cannot be applied in the lower part of its course. Notwithstanding that 

 this operation has been performed in some few cases, and with success, its performance is attended 

 with much difficulty and danger. The student will remark that in this situation, it would be 

 necessary to divide a thick muscle, and after separating the costo-coracoid membrane, the artery 

 would be exposed at the bottom of a more or less deep space, with the cephalic and axillary veins 

 in such relation with it as must render the application of a ligature to this part of the vessel 

 particularly hazardous. Under such circumstances it is an easier, and, at the same time, more 

 advisable operation, to tie the subclavian artery in the third part of its course. 



In a case of wound of the vessel, the general practice of cutting down upon, and tying it above 

 and below the wounded point, should be adopted in all cases. 



Collateral circulation after ligature of the axillary artery. If the artery be tied above the 

 origin of the acromial thoracic, the collateral circulation will be carried on by the same branches 

 as after the ligature of the subclavian ; if at the lower point, between the acromial thoracic and 

 subscapular arteries, the latter vessel, by its free anastomoses with the other scapular arteries, 

 branches of the subclavian, will become the chief agent in carrying on the circulation, to which 

 the long thoracic, if it be below the ligature, will materially contribute, by its anastomoses with 

 the intercostal and internal mammary arteries. If the point included in the ligature be below 

 the origin of the subscapular artery, the anastomoses are less free. The chief agents in restoring 

 the circulation will be the posterior circumflex, by its anastomoses with the suprascapular and 

 ucromial thoracic, and the communications between the subscapular and superior profunda, 

 which will be afterwards referred to as performing the same office after ligature of the brachial. 

 The cases in which the operation has been performed are few in number, and no published 

 account of dissection of the collateral circulation appears to exist. 



The branches of the axillary artery are 



TTT -i , D ( Superior thoracic. 



From 1st Part < . l . , Al 



( Acromial thoracic. 



v o 7 D ( Thoracica longa. 



from 2a Part m , , . 



( Thoracica alans. 



i Subscapular. 



from 3(Z Part < Anterior circumflex. 

 ( Posterior circumflex. 



The superior thoracic is a small artery, which arises from the axillary sepa- 

 rately, or by a common trunk witli the acromial thoracic. Running forwards 

 and inwards along the upper border of the Pectoralis Minor, it passes between 

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