SUPERFICIAL ANATOMY OP THE UPPER LIMB. 35 



SUPERFICIAL ANATOMY OF THE UPPER LIMB. 



THE SHOULDER. 



In the region of the shoulder, the outer part of the clavicle and the acromion 

 process of the scapula can be distinctly felt beneath the skin, and the extremity of 

 the former bone usually gives rise to a marked elevation at its junction with the 

 acromion. The rounded prominence of the shoulder is formed immediately by the 

 thick deltoid muscle, but it is also due in great measure to the large upper extremity 

 of the humerus, which can be felt moving under the muscle as the arm is rotated. 

 Close to the inner side of the shoulder-joint, and just below the clavicle, the coracoid 

 process is to be recognized in the infraclavicular fossa (see below) ; and by pressing 

 deeply in the axilla, when the arm is abducted, the lower margin of the glenoid 

 cavity and the head of the humerus are also to be felt. 



The adjacent margins of the deltoid and pectoralis major are closely united 

 together at their lower parts, so that the division between the two muscles is not 

 indicated on the surface ; but superiorly, they are separated by a triangular interval 

 of variable breadth, which gives rise to the well-marked infraclavicular fossa. By 

 pressing deeply in this fossa, the axillary artery may be compressed against the 

 second rib. The back of the shoulder is flattened, and sloped from within outwards 

 and a little forwards, owing to the oblique position of the scapula ; and the hinder- 

 portion of the deltoid, which is thinner than the anterior, is tendinous at its origin, 

 and adheres closely to the subjacent infraspinatus muscle, so that the upper part of 

 its margin is not indicated upon the surface. The infraspinatus is continued into 

 the teres minor, and below the latter muscle is the thick teres major, with the 

 latissimus dorsi winding round it, forming the posterior fold of the axilla. When 

 the arm is abducted, the middle portion of the deltoid, being brought into action, is 

 seen to present an irregular surface, the prominences corresponding to the separate 

 fleshy portions of the muscle, and the depressions to the tendinous septa extending 

 downwards from the acromion. 



The course of the axillary artery is marked upon the surface by a line drawn 

 from the mid-point of the clavicle to the inner border of the elevation formed by 

 the coraco-brachialis muscle (see below). If the limb be raised from the side, the 

 third part of the artery may be felt pulsating beneath the integument and fascia 

 (the vein intervening) as it passes into the arm, being placed at the junction of the 

 anterior and middle thirds of the space between the axillary folds. The artery may 

 be readily compressed here against the humerus. The posterior circumflex vessels 

 and the circumflex nerve are winding round the back of the humerus under cover of 

 the deltoid, at the junction of the upper and the middle thirds of the muscle. 



THE ABM. 



The shaft of the humerus is for the most part thickly covered by the muscles of 

 the arm, and can only be felt with difficulty ; but just below the insertion of the 

 deltoid the bone comes nearer to the surface, and from this spot the outer border, or 

 the external supracondylar ridge, can be followed down to the outer condyle, along 

 the bottom of a furrow over the external intermuscular septum, between the 

 supinator longus and triceps muscles. The internal supracondylar ridge is less 

 prominent, and not so readily felt. 



Along the fore and inner part of the arm (when hanging naturally by the side) 

 is the eminence formed by the biceps muscle, extending, with a slight inclination 

 outwards below, from the anterior margin of the axilla to the elbow. Superiorly, 

 this is continued into a narrow elevation produced by the coraco-brachialis muscle, 

 which issues from between the anterior and posterior axillary folds. Two 

 depressions, the inner and outer licipital furrows, are found on the inner and outer 



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