374 



THE MUSCULAK SYSTEM. 



humerus, to be inserted into a well-marked V-shaped impression above the radis 

 groove (Fig. 336, p. 376). The insertion is partly united with the tendon of th 

 pectoralis major. 



The most anterior part of the deltoid muscle is formed of parallel fibres, nc 



LEVATOR BCAPU^ uncommonly sepai 



ate from the rest c 

 the muscle at thei 

 origin from the cla 

 vicle. These fibre 

 may be continuou 

 with the trapeziu 

 over the clavicle 



Spine of scapula -^P| 



RHOMBOIDEUS MINOR 



SUPRASPINATUS 



INFRA- 

 SPINATUS 



The most posterio 

 part arises by 

 fascial origin fror 

 the spine of th 

 scapula and th 

 fascia over the in 

 fraspinatus muscle 

 These portions ar 

 attached respect 

 ively to the fron 

 and back of th 

 main tendon of in 

 sertion. The inter 

 mediate fibres ar 

 multi-pennate, attached above am 

 below to three or four septal tendon* 

 which extend for a variable distanc 

 downwards and upwards from th 

 origin and insertion of the muscle 

 The deltoid is superficial in it 

 whole extent, and forms the pro 

 minence of the shoulder. Its an 

 terior border is separated from th 

 pectoralis major by a narrow in 

 terval, in which the cephalic vei] 

 and deltoid branch of the thoraco 

 acromial artery are placed. The dee; 

 surface of the muscle, separated frorj 

 the capsule of the shoulder-join 

 by a large bursa, is related to - (l 

 the cor acoid process, associated wit! 

 which are the coraco-acromial liga 

 (tendon of insertion) men t, and the attachments of th 

 pectoralis minor, the coracobrachi 

 alis, and the short head of th' 

 biceps brachii ; (2) the capsule o 

 the shoulder -joint covering th' 

 head of the humerus, associated wit] 

 which are the long head of th< 

 biceps, and the attachments of th' 

 subscapularis, supraspinatus, infra 

 spinatus, and teres minor ; and (3 

 the proximal part of the lateral surface of the body of the humerus, associated wit! 

 which are the posterior circumflex vessels of the humerus and the axillary nerve. 



Nerve-Supply, The deltoid muscle is supplied by the terminal branches of the axillar 

 (O.T. circumflex) nerve from the fifth and sixth cervical nerves. 



Action. The main action of the deltoid is to abduct the arm, and bring the humerus int 



TRICEPS BRACHII 



EXTENSOR CARPI 

 ADIALIS BREVIS 



Olecranon 



PIG. 334. LEFT SCAPULAR MUSCLES AND TRICEPS. 



