244 Th Upper Ann 



nerve, and the brachial artery. Externally are the deltoid and supinator 

 longus. 



Dislocation of the tendon of the long head of the biceps from the 

 groove occurs in chronic osteo-arthritis, when osteophytes grow about 

 the head of the humerus. When the articular disease is further advanced 

 the tendon may be frayed out or thinned and ruptured, and adhering 

 to one of the tuberosities. (' Med. Chirurg. Trans.,' vol. Iviii.) 



The brachialis anticus arises from the front of the humerus and 

 the intermuscular septa, and is inserted into the coronoid process of 

 the ulna ; its action is, therefore, solely to bend the elbow. Its nerve- 

 supply comes from the musculo-cutaneous and sometimes also from 

 the musculo-spiral. Contracting with great energy, it may detach the 

 coronoid process, and if that process be broken off, as in dislocation 

 of the ulna backwards, some of the fibres of insertion may drag it 

 upwards. 



Relations. It is covered by the biceps, the brachial artery, and the 

 median nerve. The musculo-cutaneous nerve lies between it and the 

 biceps, and supplies them both. Its tendon lies close over the anterior 

 ligament of the elbow. 



The triceps. The long or middle head descends from below the 

 glenoid cavity ; the inner head arises from the back of the humerus 

 up to the level of the insertion of the teres major, and the outer head 

 up to the level of the teres minor. The three heads leave a passage 

 for the musculo-spiral nerve and superior profunda artery, and are in- 

 serted by a strong tendon into the top of the olecranon process, an 

 important slip running on to join the deep fascia at the back of the 

 forearm. 



The scapular head of the muscle, descending between the teres 

 minor and major, divides the area which is bounded above by the teres 

 minor, below by the teres major, and externally by the humerus into a 

 quadrilateral space through which wind the circumflex nerve and the 

 posterior circumflex vessels, and a triangular one through which the 

 dorsalis scapulae artery passes. 



A piece of the triceps is continued from the back of the external 

 condyle to the outer aspect of the olecranon under the name of 

 anconeus (p. 281). Both muscles are supplied by the musculo-spiral 

 nerve and are simple extensors of the elbow. 



THE AXILLA 



The axilla is the pyramidal space between the chest and the arm; 

 its apex reaches beneath the clavicle and into the neck. There is no 

 barrier between the root of the neck and the axilla, and pus readily 

 passes from one into the other unless escape be provided. 



Boundaries. The axilla is bounded in front by the pectoralis 

 major and minor; behind by the subscapularis, teres major, and 







