192 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 inwards be- 

 tween 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 w r ith 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 membrane, w r hich 

 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 w r ould 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 con- 

 vex 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 w r hole of the complicated move- 

 ments 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, assisted by the uvula, have the pow r er of closing the fauces com 

 pletely, 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 

 DC cut through at the lower part of the neck, and drawn upwards by di- 

 viding the loose cellular tissue which connects the pharynx to the vertebral 

 column. The saw is then to be applied behind the styloid processes, and 

 the base of the skull sawn through. The vessels and loose structure should 

 be removed from the preparation, and the pharynx stuffed with tow r or 

 \vool for the purpose of distending it, and rendering the muscle more easy 

 of dissection. The pharynx is invested by a proper pharyngeal fascia. 



The CONSTRICTOR INFERIOR, the thickest of the three muscles of this 

 class, arises from the upper rings of the trachea, the cricoid cartilage, and 

 the oblique line of the thyroid. Its fibres spread out and are inserted into 



