THE UPPER UMB 3" 



downwards with the cephalic vein between the pectoralis major and 

 deltoid, to the contiguous parts of which muscles it is distributed. 

 The clavicular branch passes upwards to end in the subclavius. 



Branches of the Second Part. — ^The inferior or long thoracic 

 artery, also called the external mammary, is directed downwards 

 and inwards along the lower border of the pectoralis minor to the 

 thoracic wall. It is distributed to the pectoral muscles, serratus 

 magnus, and intercostal muscles, and it sends branches round the 

 lower border of the pectoralis major to the mammary gland. It 

 also gives branches to the pectoral group of axillary glands, and it 

 anastomoses with branches of the aortic intercostals and internal 

 mammary. The alar thoracic artery is distributed to the axillary 

 glands. It is seldom a special branch, its place being usually taken 

 by branches of the long thoracic and subscapular. 



Branches of the Third Part. — ^The subscapular artery, which is 

 the largest of all the branches of the vessel, arises opposite the lower 

 border of the subscapularis, along which it courses downwcurds and 

 inwards to the lower angle of the scapula, in company with the long 

 subscapular ner\'e, where it anastomoses with the posterior scapular 

 and long thoracic. Besides giving branches to the muscles on the 

 posterior wall, the serratus magnus, and the posterior group of 

 axillary glands, it gives off near its origin a large branch, called the 

 dorsalis scapula. This vessel at once passes backwards through the 

 triangular space bounded above by the subscapularis, below by the 

 teres major, and externally by the long head of the triceps. There- 

 after it winds round the back of the axillary border of the scapula, 

 piercing the origin of the teres minor and groov'ing the bone, and so 

 it reaches the infraspinous fossa beneath the infraspinatus. Here 

 it breaks up into numerous branches, which supply that muscle and 

 the bone, and which anastomose with the suprascapular and dorsal 

 branches of the posterior scapular. As it passes through the tri- 

 angular space it furnishes a ventral branch (infrascapular), which 

 ramifies in the venter of the scapula beneath the subscapularis, and- 

 anastomoses with the ventral branches of the suprascapular and 

 posterior scapular. Before piercing the teres minor it gives off a 

 descending or teres branch, which passes downwards between the 

 teres maj or and minor as far as the lower angle of the scapula, where 

 it anastomoses with the terminal part of the posterior scapular. 

 The dorsalis scapulae sometimes arises directly from the axillary. 



The anterior circumflex artery, which is of small size, arises 

 from the outer side of the vessel a little below the subscapular and 

 opposite the posterior circumflex. It passes outwards in front of 

 the surgical neck of the humerus, and beneath the coraco-brachiaJis 

 and biceps. On reaching the bicipital groove it gives off an ascend- 

 ing or bicipital branch, which passes upwards in the groove with the 

 long head of the biceps, to be distributed to the shoulder- joint and 

 head of the humerus. Thereafter it continues its winding course 

 to the outer side of the bone, where it anastomoses with the pos- 

 ( terior circumflex. 



