368 



THE MUSCULAR SYSTEM. 



bounded by the iliac crest, the latissimus dorsi, and the obliquus abdominis 

 externus. This space is sometimes the site of a lumbar hernia. 



Nerve -Supply. The muscle has a single nerve the thoraco-dorsal nerve which supplies 

 it in its deep (axillary) surface. It is a branch from the posterior cord of the brachial 

 plexus (C. (6.) 7. 8.). 



Action. The main action of the latissimus dorsi muscle is to depress and rotate the 

 humerus medially, so lowering the arm as in swimming. Acting from the humerus it elevates 

 the lower ribs, and is an extraordinary muscle of inspiration. 



M. Levator Scapulae. The levator scapulae is a strap-like muscle, arising by 

 tendinous slips from the posterior tubercles of the transverse processes of the first 

 three or four cervical vertebrae, between the attachments of the scalenus medius 



in front and the splenius 

 cervicis behind. 



It is directed down- 

 wards along the side of 

 the neck, to be inserted 

 into the vertebral margin 

 of the. scapula in its 

 upper fourth, from the 

 medial angle to the spine 

 (Fig. 329). 



It is concealed in its 

 upper third by the 

 sterno - mastoid muscle. 

 Its middle third forms 



Teres minor (origin) with , f ,-1 a t> j -i 



gap for circumflex scapular part 01 the flOOr OI the 



posterior triangle. In 

 its lower third it is 

 again hidden from view 

 by the trapezius. It 

 conceals the splenius 

 cervicis and iliocostalis 



Deltoid (origin) 



Triceps brachii 

 (origin of long head) 



cervicis. 



Teres major (origin) 



Latissimus dorsi (origin) 



FIG. 329. MUSCLE- ATTACHMENTS TO THE RIGHT SCAPULA 

 (Dorsal Surface). 



Nerve - Supply. - The 

 levator scapulae has a double 

 nerve-supply : (1) from the 

 dorsal scapular nerve from 

 the brachial plexus (C. 5.), 

 which either pierces or goes 

 beneath the muscle, and (2) 

 from the cervical plexus. 

 Small branches from the 

 anterior rami of the third 



and fourth cervical nerves enter the muscle on its superficial surface near its origin. 



Action. The levator scapulae raises the superior angle and vertebral margin of the scapula, 



as in shrugging the shoulders. 



M. Rhomboideus Minor. The rhomboideus minor may be regarded as a 

 separated slip of the rhomboideus major, with which it is often continuous. It 

 arises from the ligamentum nuchce and the spines of the seventh cervical and first 

 thoracic vertebrae. 



Passing obliquely downwards and laterally it is inserted into the vertebral 

 margin of the scapula below the levator scapulae muscle, and opposite to the 

 base of the spine (Fig. 329). 



M. Rhomboideus Major. The rhomboideus major arises from the spinous 

 processes of the thoracic vertebrae from the second to the fifth inclusive, and 

 from the corresponding supraspinous ligaments. 



It also passes downwards and laterally and is inserted, below the rhomboideus 

 minor, into the vertebral margin of the scapula, between the spine and the inferior 

 angle (Fig. 329). The muscle is only inserted directly into the scapula by means 

 of its inferior fibres. Its superior part is attached to a membranous band, which, 



