MUSCLES OF TSE HEAD. 227 



_ Attachments. — By its inferior extremity it is fixed to the genial surface — 

 origin ; by its superior, it reaches the free extremity of the anterior appendix 

 of the hyoid body — termination. 



Belations. — Outwards and downwards, with the mylo-hyoideus ; inwards, 

 with its fellow, which is parallel to it ; above, with the genio-glossus. 



Action. — It draws the hyoid bone towards the anterior and inferior part 

 of the intermaxillary space. 



3. Stylo-hyoideus. 

 (Synonyms. — The hyoideus magnus of Percivall. The kerato-hyoideus magnua of Lej'h.) 



Form — Structure — Situation — Direction — Thin and fusiform, this 

 muscle, smaller than the preceding, and, like it, tendinous at both its 

 extremities, is situated on the side of the laryngo-pharyngeal apparatus and 

 the guttural pouch, behind the large branch of the hyoid bone, whose 

 direction it follows. 



Attachments. — Above, to the superior and posterior angle of the styloid 

 hone— _/ia;ed insertion; below, to the base of the cornu of the os hyoides 

 — movable insertion. 



Belations. — Outwards, with the pterygoideus internus ; inwards, with 

 the guttural pouch, the pharynx, and hypoglossal nerve. Its anterior 

 border is separated from the posterior border of the styloid bone by the 

 glosso-faoial artery and glosso-pharyngeal nerve ; along the posterior 

 border lies the npper belly of the digastricns. Its inferior tendon is 

 perforated by a ring for the passage of tho cord intermediate to the two 

 portions of the latter muscle. 



Action. — It is antagonistic to tho preceding muscle, drawing the body of 

 the hyoid bone backwards and upwards. 



4. Kerato-hyoideus. 



{Synonyms. — This is the Jiyoidem parvus of Percivall, and the small Tterato-liyoideus of 

 Leyh) 



A very small fasciculus, triangular in shape, and flattened on both sides. 

 Inserted, on one side, into the posterior border of the styloid cornu and the 

 inferior extremity of the styloid bone; and on the other', to the superior 

 border of the thyroid cornu. It responds, outwardly, to the basio-glossus 

 and the lingual artery ; inwardly, to the buccal mucous membrane. 



It approximates the cornua of the os hyoides to each other. 



5. Occipito-styloideus. 



Synonyms. — This is the muscle which, up to the present time, has been described by 

 veterinary anatomists as the stylo-hyoideus. This name has been given to the muscle 

 named by Girard the kerato-hyoideus magnus. 



A small, flat, and triangular muscle like the preceding, yet thicker and 

 more spread, filling the space comprised between the styloid process of the 

 occipital and the horizontal portion of the posterior border of the styloid 

 bone. Its fasciculi become longer as they are situated posteriorly, are 

 rather tendinous, and are carried from one of these bones to the other. 

 Outwardly, it responds to the parotid gland; inwardly, to the guttural 

 pouch which it covers for its whole extent ; its posterior border is largely 

 confounded with the superior insertion of the digastricus. When this 

 muscj^fects, it causes the os hyoides to swing, carrying its inferior extremity 

 bacMwards and downwards. 



