532 THE BLOOD-VASCULAR SYSTEM. 



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

 upward 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 incising 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. 



The vessel can be best secured by a curved incision with the convexity downward from a 

 point half an inch external to the Sterno-clavicular joint to a point half an inch internal to the 

 coracoid process. The limb is to be well abducted and the head inclined to the opposite side, 

 and this incision carried through the superficial structures, care being taken of the cephalic vein 

 at the outer angle of the incision. The clavicular origin of the Pectoralis major is then divided 

 in the whole extent of the wound. The arm is now to be brought to the side, and the upper 

 edge of the Pectoralis minor defined and drawn downward. The costo-coracoid membrane is to 

 be carefully divided on a director close to the coracoid process, and the axillary sheath exposed ; 

 this is to be opened with especial care on account of the vein overlapping the artery. The 

 needle should be passed from below, so as to avoid wounding the vein. 



In a case of wound of the vessel the general practice of cutting down upon, and tyiim 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 a 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 cir- 

 culation, 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, it will most probably also be below the 

 origins of the two circumflex arteries. The chief agents in restoring the circulation will then be 

 the subscapular and the two circumflex arteries anastomosing with the superior profunda from 

 the brachial, which will be afterward referred to as performing the same office after ligation of 

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

 published account of dissections of the collateral circulation appears to exist. 



BRANCHES OF THE AXILLARY ARTERY. 

 The branches of the axillary artery are 



XT _c . ( Superior Thoracic. ^ -, , f Long Thoracic. 



From first part | A( omial Thoracic . From second part ^ ^ Thoracic 



( Subscapular. 



From third parti Posterior Circumflex. 

 ( Anterior Circumflex. 



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

 rately or by a common trunk with the acromial thoracic. Running forward and 

 inward along the upper border of the Pectoralis minor, it passes between it and the 

 Pectoralis major to the side of the chest. It supplies these muscles and the parietes 

 of the thorax, anastomosing with the internal mammary and intercostal arteries. 



The acromial thoracic is a short trunk which arises from the fore part of the 

 axillary artery, its origin being generally overlapped by the upper edge of the 

 Pectoralis minor. Projecting forward to the upper border of the Pectoralis minor, 

 it divides into three sets of branches thoracic, acromial, and descending. The 

 thoracic branches, two or three in number, are distributed to the Serratus magnus 

 and Pectoral muscles, anastomosing with the intercostal branches of the internal 

 mammary. The acromial branches are directed outward toward the acroinion, 

 supplying the Deltoid muscle, and anastomosing, on the surface of the acromion, 

 with the suprascapular and posterior circumflex arteries. The descending or 

 humeral branch passes in the space between the Pectoralis major and Deltoid in 

 the same groove as the cephalic vein, and supplies both muscles. The artery also 

 gives off a very small branch, the clavicular, which passes upward to the Sub- 

 clavius muscle. 



The long thoracic passes downward and inward along the lower border of the 

 Pectoralis minor to the side of the chest, supplying the Serratus magnus. the 



