THE UPPER EXTREMITY. 125 



process, with the short head of the biceps and coraco- 

 brachialis attached to it, a quantity of loose cellular 

 tissue, and the capsular ligament. Severe blows upon 

 the shoulder frequently cause effusion into the bursa 

 above named, and render diagnosis of extreme difficulty, 

 and suppuration in its cavity may be mistaken for dis- 

 ease of the articulation. In the case of effusion of blood 

 into the cavity, the posterior border of the axilla will 

 become discolored a few days after the injury. 



Posterior Aspect of the Shoulder : Surface Markings. 

 The spine of the scapula is seen directly beneath the 

 skin, as a furrow in muscular persons, and as a prom- 

 inent ridge in emaciated subjects, terminating in its 

 broad acrornion process, which overhangs the articula- 

 tion. Above and below the spine are the supra- and 

 infra-spinous fossae, filled in by muscle, the superior 

 fuller than the inferior, owing to the attachment of the 

 trapezius along the upper border of the spine. The 

 inferior angle of the scapula is just beneath the surface, 

 having sometimes fibres of the latissimus dorsi attached 

 to it, which muscle, as it sweeps forward towards the 

 arm, forms the posterior border of the axilla ; occasion- 

 ally the scapula becomes dislocated over the upper edge 

 of this muscle, or rather the muscle slips beneath the 

 scapula. 



The supra-spinous fossae contains the supra-spinatus 

 muscle, between which and the bone lie the supra- 

 scapular vessels and nerve, the nerve passing below the 

 supra-scapular ligament and the vessels over it ; these 

 vessels, after supplying the supra-spinatus muscle and 

 the nerve, wind round the root of the acromion into the 

 infra-spinous fossa, and there the important inosculation 

 takes place between the dorsalis scapulae and posterior 



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