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 cornu. The anterior tendon forms a ring through which 

 plays the middle tendon of the digastricus. 



Action. It draws the body of the os hyoides backwards and 

 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 cornu, and the posterior border of the corniculum. 



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 cornicula together by their 

 superior extremities, which on contraction it approximates. 



STYLO-HYOIDEUS. 



(Fie. 71. /.) 



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

 part of the angle of the cornu, and the styloid process o* the 

 occipital bone. 



Origin. The anterior border of the styloid process. 



Insertion. The posterior part of the cornu. 



Relation. Externally 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, and 

 tongue. 



