172 MYOLOGY. 



Insertion, — ^To a small tubercle on the heel process of the os 

 hyoides. 



Relation, — ^Externally with the pterygoid muscle ; internally 

 with the pharynx, guttural pouch, and hypoglossal nerve ; the 

 glosso-facial artery and glosso-pharyngeal nerve pass between it 

 and the comu. The anterior tendon forms a ring through which 

 plays the middle tendon of digastricus. 



Action, — It draws the body of the os hyoides backwards ana 

 upwards, thus antagonising the preceding muscle ; it also assists 

 in dilating the glottis. 



HYOIDEUS PARVUS. 

 (Kerato-hyoideus Parvus.) 



Situated above and before the preceding muscle, it is small, 

 flat, and triangular. 



Origin, — From the inferior border of the anterior extremity 

 of the comu, and the posterior border of the comiculum. 



Insertion. — To the body and heel process of the os hyoides, 

 filling up the space between the three bones. 



Relation. — Externally with the hyo-glossus and the lingual 

 arteries ; internally with the mucous membrane. 



Action, — ^It approximates the three bones to which it is 

 attached. 



HYOIDEUS TRANSVERSUS. 



A short, thin muscle, joining the comicula together by their 

 superior extremities, which on contraction it approximates. 



STYLO-HYOIDEUS. 

 (Fig. 71./.) 



Flat and triangular, it fills up the space between the posterior 

 part of the angle of the comu, and the styloid process of the 

 occipital bone. 



Origin, — The anterior border of the styloid process. 



Insertion. — The posterior part of the comu. 



Relation. — Extemally with the parotid gland, and internally 

 with the guttural pouch. Its posterior fibres blend with those of 

 the origin of the digastricus. 



Action. — It draws back and depresses the os hyoides. 



