BACK OF THE A 11 M . 139 



the remains of the deltoid muscle, overlapping its anterior 

 half, must be removed. It arises from the walls of the 

 infra-spinous fossa, and from the fascia which covers it ex- 

 ternally ; it is inserted into the middle facet of the greater 

 tuberosity of the humerus by a tendon which forms part of 

 the capsular ligament of the shoulder-joint. Its tendon is 

 at first concealed by the muscular fibres which overlap it, 

 each half of the muscle being folded over the tendon, from 

 which the fibres diverge in a bipenniform manner. Passing 

 along its outer border is the posterior scapular artery, a 

 branch of the subclavian ; at the inferior angle of the 

 scapula this artery inosculates with the subscapular, and 

 by the offsets which it sends to the infra-spinatus muscle 

 and fossa, unites with the terminal twigs of the supra- 

 scapular. 



The TERES MINOR MUSCLE lies between the infra-spinatus 

 and the teres major muscles ; it is closely connected with 

 the former, and can only be separated from it artificially, 

 so that the dissector is sometimes at a loss to define this 

 muscle, though he may be perfectly aware of its locality. 

 It arises from the inferior border of the scapula, and is in- 

 serted into the lower facet of the greater tuberosity of the 

 humerus, its tendon forming part of the capsular ligament 

 of the shoulder-joint. The dorsal branch of the subscapular 

 artery curves around this muscle, just outside the scapular 

 head of the triceps muscle, and passes to the infra-spinous 

 fossa, beneath the infra-spinatus muscle, which it supplies, 

 and where it inosculates with the terminal branches of the 

 supra-scapular. 



BACK OP THE ARM. 



The TRICEPS EXTENSOR CUBITI MUSCLE makes up the 

 whole bulk of the back of the arm ; it has three points of 

 origin, known as its long, middle, and short heads. The 

 long head arises from the inferior border of the scapula, 

 just below the glenoid cavity ; the middle head arises from 

 all the shaft of the humerus below its greater tuberosity, 

 and from the external condyloid ridge and the intermuscu- 

 lar septum connected with it ; the short head arises from 

 the shaft of the humerus below the insertion of the teres 

 major, and from the internal condyloid ridge and its inter- 

 muscular septum. These three heads conjoin, to be inserted 

 by a broad aponeurotic tendon into the olecranon process 



