MYOLOGY 97 



Shape. Thin, triangular. 



Relations. Superiorly, with the skin. The most superficial of the 

 dorsal muscles. 



Action. To elevate the humerus and thus flex the shoulder-jomtr 

 An expiratory muscle when the wing is fixed. 



Trapezius (Fig. 19, No. 20). Location. In the shoulder region, 

 just below the longissimus dorsi. 



Origin. From the neural spines of the second, the third, the fourth, 

 and the fifth cervical vertebrae just below the latissimus dorsi. 



Insertion. To the mesian upper border of the scapula. 



Shape. A flat oblong layer of fibers. 



Relations. The posterior part of the trapezius overlies the an- 

 terior part of the rhomboideus. The posterior two-thirds is covered 

 by the latissimus dorsi. The anterior third is superficial. 



Action. Draws the scapula forward. 



Rhomboideus (Fig. 19, No. 19). Location. Supero-posterior 

 scapular region. 



Origin. From the neural spines of the first four dorsal vertebrae 

 beneath the latissimus dorsi and trapezius muscles. 



Insertion. The fibers passing outward and backward attach to the 

 posterior third of the mesial or upper border of the scapula. 



Shape. Thin, flat, delicate. 



Relations Superiorly, by the latissimus dorsi and the trapezius. 



Action. To draw the free end of the scapula upward and 

 forward. 



Serratus Magnus Anticus (Fig. 13, No. 16). Location. The 

 supero-lateral side of the thorax. 



Origin. By three strong digitations: first, from the outer part of 

 the second true rib just above the base of the epineural appendage; 

 the other two, from similar locations on the two succeeding ribs, 

 just above the origin of the dermo-ulnaris. 



Insertions. The first by tendinous attachment to the interpleura- 

 pophysial membrane. The rest of the fibers pass upward and 

 slightly forward, and are inserted to the inferior surface of the 

 apex of the scapula. 



Shape. Three flat, strong digitations. 



Relations. Internally, with the ribs. 



Action. If the scapula is fixed, it is a muscle of inspiration. 



Serratus Parvus Anticus. Location. The outer and upper sur- 

 face of the anterior part of the thorax. 



