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- joint. 

 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 sutf ace of the 

 apex of the scapula. 



Shape. — Three fiat, strong digitations. 



Relations. — Internally, with the ribs. 



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



Serratus Parvus Anticus. Location. — T^he outer and upper sur- 

 face of the anterior part of the thorax. 

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