MUSCLES OF THE PHARYNX. 165 



The stylo-glossus arises from the apex of the styloid process, and 

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

 tongue into two portions, one transverse, which passes transversely 

 inwards between the two portions of the hyo-glossus, 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 

 surface 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 isthmii 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. 



Fifth Group. Muscles of the Pharynx. 



^ Consteictor 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 

 upwards by dividing the loose cellular tissue which connects the 



* Called also constrictor isthmii faucium. G. 



