THORACIC BRANCHES OP AXILLARY ARTERY. 395- 



follows, viz., behind it, the circumflex and musculo-spiral ; to its inner 

 side, the ulnar and the two internal cutaneous ; to the outer side, the 

 external cutaneous and median. The external cutaneous and the 

 circumflex nerves leave the artery in the axilla, and at the lower part 

 of the axilla median nerve is often before the vessel ; in an operation, 

 that nerve might serve as a guide to the position of the artery, for it 

 could be distinguished from the other large nerves (ulnar and musculo- 

 spiral) by the circumstance of its being the nearest to the pectoral 

 muscle. Beyond the border of the pectoralis major, the artery is 

 covered only by the skin and fascia on the inner side ; and here the 

 flow of blood may be controlled by pressure of the finger directed out- 

 wards against the humerus. 



BEANCHES OF THE AXILLARY ARTERY. 



The branches of the axillary artery consist of the external thoracic 

 branches furnished to the muscles of the chest, the subscapular branch 

 to the shoulder, and the anterior and poster ior circumflex branches to 

 the upper part of the arm. The branches are not constant in their 

 number, size, or mode of origin. 



1. The short thoracic artery (thoracica suprema), a branch of incon- 

 siderable size, arises at a point internal to the pectoralis minor muscle, 

 and inclines downwards and inwards across the first two intercostal 

 spaces, anastomosing with the internal mammary and intercostal 

 branches contained in them, and terminates between the pectoral 

 muscles. 



2. The acromio-thoracic axis (art. thoracica humeraria), of consider- 

 able size, and by far the most constant of the thoracic branches of the 

 axillary, arises from its forepart at the inner border of the pectoralis 

 minor muscle, and soon divides into branches which take dififerent 

 directions. 



(</) The acromial branches pass partly to the deltoid muscle and partly to the- 

 upper surface of the acromion, and anastomose with the suprascapidar and 

 posterior circumflex arteries. 



(/;) The humeral branch passes do-mi in the interval between the pectoralis 

 major and deltoid muscles, and is distributed to their margins ; it is accompanied 

 by the cephalic vein. 



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

 muscles, and anastomose with the other thoracic arteries. 



{(1) The clavicular branch, very small, passes inwards to the subclavius 

 muscle. 



3. The long thoracic or external mammary artery is directed down- 

 wards and inwards, along the lower border of the pectoralis minor, and 

 is distributed to the mamma, and to the serratus and pectoral muscles, 

 and anastomoses with the external branches of the intercostal arteries. - 



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

 being frequently wanting, and having its place supplied by branches 

 from the thoracic and subscapular arteries. It is distributed to the 

 lymphatic glands and the fatty tissue in the axilla. 



5. Subscapular Artery. — This branch, the largest given off by the 

 axillary artery, arises close to the lower border of the subscapular 

 muscle, along which it proceeds downwards and backwards, towards 



