THE BEACHIAL AETEEY. 917 



(4) Arteria Subscapularis. The subscapular artery is the largest branch 

 >f the axillary artery. It arises from the third part of the artery, opposite the 

 ower border of the subscapularis, along which it descends, giving branches to 



',he muscle and to the medial wall of the axillary space. After a short course 

 t divides into two terminal branches, the circumflexa scapulae and the thoraco- 

 lorsalis. 



(1) The circumflex scapulae is frequently the larger branch. It arises about 37 mm. 

 one and a half inches) from the commencement of the subscapular trunk, and passes 

 mck wards into the triangular space which lies between the subscapularis above, the teres 

 najor below, and the long head of the triceps laterally. Turning round, and usually groov- 

 ng the axillary border of the scapula, under cover of the teres minor, it enters the infra- 

 ipinous fossa, where it breaks up into branches which anastomose with branches of the 



Descending branch of the transverse cervical artery and the transverse scapular arteries. 

 tVhilst it is in the triangular space the artery gives off an infrascapular branch which 

 jasses into the subscapular fossa and terminates by anastomosing with the branches of 

 1 he descending branch of the transverse cervical and the transverse scapular arteries. 

 t gives off, in the same situation, a descending branch also, which runs downwards, to 

 he lower angle of the scapula, between the teres major and minor muscles, and small 

 >ranches are given to the deltoid and long head of triceps. 



(2) The thoraco-dorsal continuation of the subscapular trunk accompanies the thoraco- 

 lorsal nerve (O.T. long subscapular) along the axillary border of the scapula to the wall 

 >f the thorax, where it anastomoses with the lateral thoracic artery and with branches 

 /f the intercostal arteries. 



(5) Arteria Circumflexa Humeri Posterior. The posterior circumflex artery 

 irises from the third part of the axillary artery and passes backwards, accompanied 

 )y the axillary nerve, through an intermuscular cleft, the so-called quadrilateral 



jpace, which is bounded by the teres minor and snbscapularis above, the teres 

 najor below, the long head of the triceps medially, and the humerus laterally. It 

 i ;urns round the surgical neck of the humerus, under cover of the deltoid muscle, 

 ind terminates in numerous branches which supply the deltoid. As a rule it 

 i s an artery of large size, only slightly smaller than the subscapular. 



Branches. (a) Muscular to the teres major and minor, the long and lateral heads 



)f the triceps, and the deltoid; (6) An acromial branch, which ascends to the 

 juoomion, where it anastomoses with the acromial branches of the transverse scapular 

 .uid the thoraco-acromial arteries; (c) A descending branch, which runs distally, along 



he lateral head of the triceps, to anastomose with the profunda artery ; (d) Articular 

 ^o the shoulder-joint; (e) Nutrient to the head of the humerus; (/) Terminal, which 



.upply a large portion of the deltoid, and anastomose with the anterior circumflex and 



.horaco-acromial arteries. 



(6) Arteria Circumflexa Humeri Anterior. The anterior circumflex artery is 

 i small branch ; it is given off from the third part of the axillary close, to, or 

 n common with, the posterior circumflex. It passes laterally, posterior to the 

 joraco-brachialis and the two heads of the biceps, round the front of the surgical 

 leek of the humerus, and it terminates by anastomosing with the posterior circum- 



At the intertubercular groove it gives a well-marked branch which accom- 

 panies the tendon of the long head of the biceps, supplying the sheath of the 

 oendon, and giving branches to the shoulder-joint. It also gives muscular 

 3ranches to the adjacent muscles, one of which runs distally along the tendon 

 if insertion of the pectoralis major. 



AETERIA BEACHIALIS. 



The brachial artery is the direct continuation of the axillary. It com- 

 mences at the lower border of the teres major, and ends, in the cubital fossa, at 

 the level of the neck of the radius, by dividing into the radial and uluar arteries. 

 The general course of the brachial artery is distally and laterally, along the 

 dial side of the arm, at first on the medial side and then in front of the 

 umerus. Its position and that of the axillary artery may be indicated on the 



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