188 MUSCLES OF THE PHARYNX. 



The STYLO-GLOSSUS arises from the apex of the styloid process, and 

 from the stylo-maxillary ligament ; it divides upon the side of the 

 tongue into two portions, one transverse, which passes transversely 

 in wards between the two portions of the hyo-glosssus, and is lost among 

 the transverse fibres of the substance of the tongue, and another 

 longitudinal, which spreads out upon the side of the tongue as far 

 as its tip. 



Relations. By its external surface with the internal pterygoid 

 muscle, the gustatory nerve, the parotid gland, sublingual gland, and 

 the mucous membrane of the floor of the tongue. By its internal sur- 

 face with the tonsil, the superior constrictor muscle of the pharynx, 

 and the hyo-glossus muscle. 



The PALATO-GLOSSUS passes between the soft palate, and the side 

 of the base of the tongue, forming a projection of the mucous mem- 

 brane, which is called the anterior pillar of the soft palate. Its fibres 

 are lost superiorly among the muscular fibres of the palato-pharyngeus, 

 and inferiorly among the fibres of the stylo-glossus upon the side of the 

 tongue. This muscle with its fellow constitutes the constrictor isthmi 

 faucium. 



Actions The genio-hyo-glossus muscle effects several movements of 

 the tongue, as might be expected from its extent. When the tongue 

 is steadied and pointed by the other muscles, the posterior fibres of the 

 genio-hyo-glossus would dart it from the mouth, while its anterior 

 fibres would restore it to its original position. The whole length of 

 the muscle acting upon the tongue, would render it concave along the 

 middle line, and form a channel for the current of fluid towards the 

 pharynx, as in sucking. The apex of the tongue is directed to the 

 roof of the mouth, and rendered convex from before backwards by the 

 linguales. The hyo-glossi, by drawing down the sides of the tongue, 

 render it convex along the middle line. It is drawn upwards at its 

 base by the palato-glossi, and backwards or to either side by the stylo- 

 glossi. Thus the whole of the complicated movements of the tongue 

 may be explained, by reasoning upon the direction of the fibres of the 

 muscles, and their probable actions. The palato-glossi muscles as- 

 sisted by the uvula, have the power of closing the fauces completely, 

 an action which takes place in deglutition. 



Fifth Group. Muscles of the Pharynx. 



Constrictor inferior, 

 Constrictor medius, 

 Constrictor superior, 

 Stylo-pharyngeus, 

 Palato-pharyngeus. 



Dissection. To dissect the pharynx, the trachea and oesophagus 

 are to be cut through at the lower part of the neck, and drawn up- 

 wards by dividing the loose cellular tissue which connects the pharynx 

 to the vertebral column. The saw is then to be applied behind the 



