DISSECTION OP THE HEAD AND NECK. 211 



articulation of the two cornua. Preserve the 9th nerve at the posterior 

 edge of the great cornu, and the pharyngeal artery passing beneath it. 



The Palato-phabyngeus has already been in part dissected with the 

 muscles of the soft palate. See page 209. 



The Pteeygo-pharyngbds. This muscle arises from the pterygoid 

 process, from which point its fibres diverge to the upper and lateral 

 aspect of the forepart of the pharynx. At its lower edge its fibres are 

 parallel to, and with difficulty separated from, those of the palato- 

 pharyngeus. Its outer surface is constantly covered by a layer of fattj^ 

 elastic tissue. 



The Hyo-phaeyngbus, origin — thyroid cornu of the hyoid bone. 



The Thyeo-pharyngbus, origin — thyroid cartilage. 



The Ceico-pharyngeus, origin — cricoid cartilage. 



These three muscles succeed one another in the order named, the first 

 mentioned being the most anterior. They pass upwards over the side of 

 the pharynx, and terminate on the middle line of its roof. 



The Stylo-pharyngbus. This is a thin, strap-like muscle arising 

 from the inner siirface of the great cornu of the hyoid bone near its 

 upper extremitj'. It descends to the pharynx, and expands on it at the 

 outer edge of the pterygo-pharyngeus. 



The Small Stylo-phary'NGeus. This muscle is not constant, though 

 frequently present. It is a delicate, worm-like muscle arising from the 

 inner surface of the great cornu, about an inch above its lower extremity. 

 It passes upwards on the pharynx at the anterior edge of the hyo- 

 pharyngeus. 



The Aeytbno-phaeyngbus. This muscle will not be seen at present. 

 It is a small slip arising from the arytenoid cartilage, and passing to the 

 pharynx at its junction with the oesophagus. 



Actio7i of the Pharyngeal Muscles. — The stylo-pharyngeus dilates the 

 anterior part of the pharynx for the reception of the bolus. All the 

 other muscles are constrictors, grasping in succession the bolus, and 

 carrying it on to the oesophagus. 



The Cerato-hyoid {Hyoidem parvus of Percivall) (Plate 33). This 

 muscle is most conveniently dissected at this stage, and it is therefore 

 here described although not belonging to the pharynx. It is a small 

 flat muscle occupying the angle between the small and the thyroid 

 cornu of the hyoid bone. It arises from the posterior edge of the small 

 cornu, and from the great cornu immediately above the intercornual 

 articulation. It is inserted into the upper edge of the thyroid cornu. 

 The lingual artery, in crossing down to the base of the tongue, passes 

 over the muscle. 



Action. — To elevate the thyroid cornu and with it the larynx. 



The Pharyngeal Artery. This is a small branch of the submaxillary 

 which passes beneath the great cornu, crossing either outwardly or 



