212 THE ANATOMY OF THE HORSE. 



inwardly the 9th nerve. It gives branches to the pharynx, and is con" 

 tinued to the soft palate. 



The 9th or Glossopharyngeal Nerve descends on the guttural 

 pouch, behind the great cornu ; and, crossing to the inner side of the 

 external carotid artery, it 'gives off its pharyngeal branch. This turns 

 round behind the stylo-pharyngeus muscle, and ramifies on the pharynx, 

 meeting there the pharyngeal branches of the 10th and sympathetic 

 nerves, and forming with them the pharyngeal plexus. 



Nerve to the Stylo-pharyngeus. — This is a special branch of the glosso- 

 pharyngeal, given off either from the trunk of the nerve or from its 

 glossal continuation. It enters the muscle at the middle of its outer 

 face. 



The Glossal Continuation of the 9th nerve passes over the hyo-pha- 

 ryngeus and palato-pharyngeus to reach the base of the tongue ; and in 

 its course it detaches fibres which are probably motor to the palato- 

 pharyngeus, hyo-pharyngeus, cerato-hyoid, and hyoideus transversus. 



For the pharyngeal branches of the 10th and sympathetic nerves see 

 pages 199 and 200. 



Directions. — The pharynx is to be opened by an incision along its 

 lateral aspect, w 7 hen, by hooking back the edges of the incision, a view 

 of its interior will be obtained. 



The Pharyngeal Cavity (Fig. 27, page 223) is irregularly tubular in 

 form, and presents seven openings. These are : — 



1. The Isthmus of the Fauces, already described (page 208). 



2. The Superior Nares (2), situated vertically over the isthmus, from 

 which they are separated by the soft palate. They are wide, gaping 

 orifices, with rigid bony margins. 



The Lower Openings of the Eustachian Tubes (2), which are situated 

 on the sides of the pharynx, behind and in line with the superior nares. 

 The opening has the form of a vertical slit, the outer edge of which 

 contains the cartilaginous extremity of the tube. 



4. The Tipper Aperture of the Larynx. — This is placed on the floor of 

 the pharynx, and has the form of a pitcher-mouth. During deglutition 

 the epiglottis is folded over it like a lid, but at other times it is a large 

 patent orifice. 



5. The (Esophageal Orifice. — At the posterior end of the pharynx, its 

 cavity is continued into the lumen of the gullet. Except during the 

 passage of solids or fluids, however, this orifice is not open. 



Mucous Membrane. — This lines the cavity completely, and is con- 

 tinuous through the before-mentioned orifices with the lining membrane 

 of the mouth, nasal chambers, Eustachian tubes and guttural pouches, 

 larynx, and oesophagus. It has a stratified squamous epithelium, except 

 in its upper and anterior part, where it is ciliated. It has many mucous 

 glands. 



