SHOULDER AND ARM. 



the interval between the olecranon and internal condyle. It 

 supplies the skin of the armpit and back of the arm internally 

 as far as the elbow. It joins the lesser internal cutaneous and 

 communicates with the posterior part of the lateral branch of 

 the third intercostal. [636] 



ARTERIES. 



Axillary. Beginning at the outer border of the first rib as 

 a continuation of the subclavian, this runs downward and 

 slightly outward along the outer wall of the axilla, internal to 

 the humerus ; it becomes the brae hi al at the lower border of the 

 Teres major. It is arbitrarily divided into three parts, the 

 first above, the second behind, and the third below the Pec- 

 toralis minor. It lies external to the axillary vein; the cords 

 and branches of the brachial plexus lie closely behind it, at its 

 sides, and (third part) in front of it. Its branches are as fol- 

 lows: [827] 



Superior Thoracic. A small branch from the first part, run- 

 ning downward and inward on the first intercostal space. 

 Acromio-thoracic : A short branch from the second part which 

 runs forward over the upper border of the Pectoralis minor and 

 divides into four branches, viz.: clavicular, to the sterno- 

 clavicular joint; pectoral, descending between the two pec- 

 toral muscles; humeral, descending in the groove between the 

 Deltoid and Pectoralis major; and acromial, crossing the 

 coracoid process to the acromion. Long thoracic: A branch 

 from the second part which descends along the lower border 

 of the Pectoralis major and often (external mammary artery) 

 supplies the mammary gland. Alar thoracic: A branch, or 

 branches, of irregular origin, to the axillary glands. Subscap- 

 ular: A large branch from the third part which descends along 

 the lower border of the Subscapularis with the long subscapu- 

 lar nerve ; a branch (dorsalis scapulae) runs through the trian- 

 gular space between the Supscapularis, Teres major, and Triceps 



[165] 



