432 THE ARTERIES OF THE UPPER LIMB. 



major and minor muscles ; the vein is on its inner side ; and the three cords of the 

 'brachial plexus are placed, one on the outer side, the second behind, and the 

 third on the inner side, the last, together with the internal anterior thoracic nerve, 

 intervening between the artery and vein. 



The third part of the axillary artery is covered anteriorly for the upper half of 

 its extent by the pectoralis major muscle ; in its lower half it is superficial, being 

 placed immediately beneath the deep fascia of the arm, and here the flow of blood 

 in the vessel may be readily controlled by pressure directed from within outwards 

 against the humerus. It rests upon the subscapularis muscle and the tendons of the 

 latissimus dorsi and teres major ; and on its outer side is the coraco-brachialis 

 muscle. 



The axillary vein is still on its thoracic side, and the lower portion of the artery 

 is accompanied also by one or both of the Irachial venae, comites. The nerves result- 

 ing from the division of the brachial plexus are disposed around the artery as follows, 

 viz., behind are the circumflex andmusculo-spiral; to its inner side ft\Qiilnar (between 

 the artery and vein), and the small internal cutaneous (internal to the vein) ; to its 

 outer side the external cutaneous and median ; while the large internal cutaneous is 

 usually in front of the artery, and the inner head of the median crosses it obliquely 

 from within outwards. 



BRANCHES. The branches of the axillary artery are very variable in their 

 number, size, and mode of origin. They comprise thoracic branches furnished J.o 

 Jhejnuscks of the chest, the sulscapular branch tolhe shoulder, and two circumflex 

 branches to the upper part of the arm. Small irregular twigs are also given to the 

 serratus magnus, subscapularis and coraco-brachialis muscles, and to the skin. One 

 more constant branch passes through the loop formed by the two heads of the 

 median nerve to the pectoral muscles and the upper part of the biceps, and is often 

 continued downwards to anastomose with the bicipital branch of the brachial 

 artery. 



1. The superior or short thoracic artery is a small branch, which arises 

 near the lower border of the subclavius muscle. It inclines downwards and inwards 

 across the first intercostal space, and terminates in the two pectoral muscles, giving 

 off also branches which supply the upper part of the serratus magnus and the sub- 

 jacentjnte^c^staljnuscles, and anastomose with the intercostal arteries. 



~~2. The acromio-thoracic artery, of considerable size, and the most constant 

 of the thoracic branches of the axillary artery, arises from its fore part at the upper 

 border of the pectoralis minor muscle, and soon divides into branches which take 

 different directions. 



(a) The acromial branches pass partly to the deltoid and partly through that 

 muscle to the upper surface of the acromion, forming anastomoses with the supra- 

 scapular and posterior circumflex arteries. 



(b) The descending or humeral branch passes down in company with the cephalic 

 vein in the interval between the pectoralis major and deltoid muscles, and is distri- 

 buted to their margins, and to the integument. 



(c) The thoracic branches are distributed to the serratus magnus and pectoral 

 muscles, and anastomose with the other thoracic arteries. 



(d) The clavicular branch, very small, passes upwards to the subclavius muscle. 



3. The long thoracic artery (external mammary) is directed downwards and 

 inwards, along the lower border of the pectoralis minor, and is distributed to the 

 serratus and pectoral muscles, and to the mamma, forming anastomoses_\vith_branches 

 of the intercostal arteries. 



4. The alar thoracic branch is a very small vessel and not constant, its place 

 being frequently supplied by branches from the thoracic and subscapular arteries. 

 It is distributed to the lymphatic glands and the fatty tissue in the axilla. 



