'Luxation of Scapula' 241 



The subclavian fossa corresponds to the interval between the 

 borders of the pectoralis major and deltoid at their clavicular origin ; 

 the greater the muscular development, the narrower this crevice. In 

 its depths may be felt the apex of the coracoid process, to the thoracic 

 aspect of which the narrowest part of the pectoralis minor is passing. 

 The second part of the axillary artery is beneath the lesser pectoral, 

 the first part being between its upper border and the outer edge of the 

 first rib. To the inner side of the artery is the vein, and to the outer 

 are the two cords of brachial plexus. 



The serratus magnus arises by nine digitations from the eight 

 upper ribs, and, hugging the chest-wall, is inserted into the thoracic 

 aspect of the vertebral border of the scapula. The muscles bounding 

 the axilla anteriorly and posteriorly enclose it in front and behind, 

 and the axillary vessels and the cords of the plexus, in their passage 

 from the root of the neck, cross over the highest part of the muscle. 



Its nerve-supply is from the nerve of Bell (p. 251), which descends 

 upon its axillary surface. 



The action of the muscle is to steady the shoulder-blade, to draw 

 it forwards, and to keep its vertebral border and inferior angle close 

 against the chest. In paralysis of the muscle the angle of the scapula 

 projects like a rudimentary wing, and the fingers can be thrust up 

 between it and the chest-wall almost to the glenoid cavity. This 

 condition was formerly called ' luxation of the scapula. 1 Over-action 

 of the muscle is the usual cause of the paralysis I have met with it in 

 a nurse who spent most of her time in rubbing an old lady with 

 chronic pleurisy, and in a girl who was skipping all day long. When 

 the patient is told to raise the arm over the head the scapula is drawn 

 upwards and inwards by the elevator and by the rhomboids, for there 

 is nothing to keep it down to the side ; and, as the shoulder-blade 

 cannot be rotated, the superior angle fails to be tilted upwards and 

 the attempt at raising the arm fails. 



The deltoid arises from the front of the clavicle, the acromion 

 process, and the lower border of the spine of the scapula, and is in- 

 serted halfway down the outer surface of the humerus. It is supplied 

 by the circumflex nerve and is sometimes paralysed after dislocation 

 of the humerus ; the power of abduction being then lost. 



Relations. It is covered by the skin and fasciae. Its inner border 

 rests against the outer edge of the pectoralis major, and in the groove 

 between these muscles lie the cephalic vein and the descending 

 branch of the acromial thoracic artery. Beneath it is a large bursa 

 which separates it from the shoulder-joint. The deltoid covers also 

 the coracoid process and its muscles, namely the pectoralis minor, 

 coraco-brachialis, and short head of biceps ; the coraco-acromial 

 ligament ; the upper end of the humerus with the subscapularis 

 inserted into the inner (lesser) tuberosity, and the supra- and infra- 

 spinatus and the teres minor into the greater ; the bicipital groove, 



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