THE SHOULDER 



1153 



tondon. Thus the continuity of the capsule is interrupted by two and sometimes 

 three apertures. 



The shaft of the humerus is wt-ll covered by muscles in the greater part of 

 its extent, especially alxtve. Below tlie insertion of the deltoid, the outer border 

 of the bone can be traced downwards into tlie external supracondyloid ridge. The 

 inner border and ridge are less prominent. Attaeiied to these ridges and borders 

 are the intermuscular septa, each lying between the triceps and brachialis anticus, 

 and the outer one giving origin to the brachio-radialis (supinator longus; and 

 extensor carpi radialis longior as well. The outer septum is perforated by the 



Fig. 716.— Back View of the Scapular Muscles and Triceps. 



Supra-spinatus 



Iafra-spiaatu3 

 Teres minor 



Teres major 



Long head of triceps 



Outer head of triceps 



Inner head of 



superior profunda vessels and the musculo-si)iral nerve, the inner by the inferior 

 profunda and anastomotica magna arteries and tlie ulnar nerve. On either side 

 of the well-known prominence of the biceps is a furrow. Along the outer ascends 

 the cephalic vein. The inner corresponds t<» the line of the basilic vein which lies 

 superficial to the deep fascia below the middle of tlie arm, and superficial and 

 internal to the brachial vessels and median nen-e. 



A line drawn along the inner edge tif the biceps from the insertion of the 



teres major to the middle of the bend of the elbow corresponds to the brachial 



artery. In the u]tper two-thirds, this artery can be comj^ressed against tlie bone 



by pressure outwards; in its lower third the humerus is behind it. and })ressure 



73 



