358 



THE MUSCULATURE 



The levator scapulae and the serratus anterior (magnus) are two differentiated parts of a 

 muscle which is a continous mass in many of the lower mammals. A muscle corresponding 

 to the rhomboideus is found in some of the reptiles and many of the higher vertebrates. In 

 some of the mammals it has a more extensive cervical attachment than in man. 



FASCIA 



The fasciae investing these muscles are shown in cross-section in fig. 357. 



The levator scapulae is invested by fascial membranes, the external and stronger of which 

 is continued dorsally from the fascial investment of the scalene muscles. The thinner layer 

 on its deep surface hes next the fascial investment of the intrinsic muscles of the back. Cranial- 

 ward from the rhomboid muscles the fascial investment of the levator scapulae is fused dorsally 

 with the fascia covering the splenius cervicis. Where the dorsal margin of the levator comes 

 in contact with the rhomboideus minor, the fascia is continued over into the thin fascial mem- 



FiG. 354. — Serratus Anterior. 



Upper part of 

 serratus anterior 



Middle part 





brane which invests both surfaces of the rhomboidei. Similarly the investing fascia of the leva- 

 tor is continued ventrally into the fascia investing both surfaces of the serratus anterior (mag- 

 nus; . Within the internal fascial investment of this group of muscles, near the insertion of 

 the levator, run the transversa colli artery and the dorsal scapular nerve. 



MUSCLES 



The rhomboideus minor (fig. 353). — Origin. — Lower part of the ligamentum nuchse, the 

 spines of the seventh cervical and first thoracic vertebrae, and the intervening supraspinous liga- 

 ment. Insertion. — Vertel^ral border of the scapula near the spine. 



The rhomboideus major (fig. 353). — Origin. — Spines of the first four or five thoracic ver- 

 tebra;. Insertion. — Vertebral border of the scapula opposite the infraspinous fossa. 



Structure. — The two muscles are included between two adherent fascial layers which bridge 

 over the greater or less si)acc that may intervene between them. The fibre-bundles take a 

 parallel course oltliquely downward and lateralward from the vertebrae. From the vertebral 

 spines the muscles arise by an aponeurosis which varies in widtli. The attachment to the scap- 

 ula is by short tendinous processes. The attachment of the rhomboideus major is firmest to- 

 ward the inferior angle of the scapula. 



Nerve-supply. — The dorsal scapular nerve, which usually arises chiefly from the fifth 

 cervical nerve, enters the superior margin of tne rhomboideus minor and then courses distally 

 near the deep ventral surface of the two muscles and about midway between the tendons of 

 origin and in.scrtion. 



