314 THE MUSCULAR SYSTEM. 
downwards. The latissimus dorsi acting alone, besides rotating the limb, draws it inwards and 
backwards, as in the act of swimming. 
-FASCLEA AND MUSCLES OF THE SHOULDER. 
The deep fascia covering the scapular muscles presents no feature of special 
importance. Attached to the clavicle, acromion, and scapular spine, it is thin over 
LEVATOR ANGULI SCAPUL 
TRAPEZIUS ——— SS S SUPRASPINATUS 
Scapular spine (cut) 
INFRASPINATUS 
RHOMBOIDEUS a = 
MAJOR} pe et = = - TERES MINOR 
Infraspinous 
fascia 
Dorsal scapular 
artery (branch of) 
TERES MAJOR DELTorp (reflected) 
Cutaneous branch 
Y of circumflex 
po: ee NN __ TRICEPS (outer 
head) 
Pt tenet TRICEPS (long head) 
‘Musculo-spiral nerve 
TRICEPS (outer head) 
BRACHIALIS ANTICUS 
Triceps (inner head) 
External intermuscular 
septum 
External cutaneous branches 
of musculo-spiral nerve 
the deltoid muscle. Below the 
deltoid it is thicker; it gives 
origin to the infraspinatus 
muscle, and is continuous with 
the fascie of the axilla and the 
back. 
The muscles proper to the 
shoulder comprise the deltoid, Um 
nerve 
BRACHIO-RADIALIS 
EXTENSOR CARPI RADIALIS 
LONGIOR 
ANCONEUS 
supraspinatus, infraspina- f | 
tus, teres minor, teres major, and Frexor IW \ a ar (oomadonreen do) er 
subscapularis. They surround, ,. vin \\ \ . | 
and along with other muscles, \ | 
act on the shoulder joint. Fig. 234.—DELT0ID REGION AND Back OF THE ARM. 
The deltoid, a coarsely fas- 
ciculated, multipennate muscle, has an extensive origin from (1) the front of | 
the clavicle in its outer third; (2) the outer border of the acromion process ; 
and (3) the lower border of the spine of the scapula. Its origin embraces | 
the insertion of the trapezius. The fibres of the muscle converge to the outer 
side of the shaft of the humerus, to be inserted into a well-marked V-shaped 
impression above the spiral groove. The insertion is partly united with the 
tendon of the pectoralis major. The deltoid is superficial in its whole extent, 
and forms the prominence of the shoulder. Its anterior border is separated from 
the pectoralis major by a narrow interval, in which the cephalic vein and humeral 
FS . 
