950 THE DIGESTIVE SYSTEM. 
The vessels of the palate are derived from the posterior palatine artery, which runs forwards 
on the hard palate close to the alveolar border, and from the ascending palatine branch of the 
facial, which accompanies the levator palati to the soft palate. 
The nerves—all branches of Meckel’s ganghon—are: the large posterior palatine, which 
descends through the posterior palatine canal and runs forward on the hard palate with the 
posterior palatine artery ; the naso-palatine, which passes down through the foramen of Scarpa 
and reaches the front of the hard palate ; and the small posterior and accessory posterior palatine 
nerves, which run through the accessory palatine canals and supply the soft palate. 
Fauces or Isthmus of the Fauces (isthmus faucium).—This is the aperture 
through which the mouth communicates with the pharynx (Fig. 638). It is bounded 
at the sides by the anterior palatine arches, above by the under surface of the soft 
palate, and below by the dorsum of the tongue; in width it corresponds pretty 
closely to the cavum oris. 
The anterior palatine arches (arcus glosso-palatinus), often known as the anterior 
pillars of the fauces, are two prominent folds of mucous membrane, containing the 
palato-glossus muscles in their interior, which bound the isthmus of the fauces 
laterally (Fig. 638). Springing above from the under surface of the soft palate, a 
little way (about 8 mm.) in front of its free edge, and near the base of the uvula, 
they pass downwards and slightly forwards to join the tongue a little behind the 
middle of its lateral border. 
The posterior palatine arch is described with the pharynx (p. 984). 
THE TONGUE. 
The tongue (lingua) is a large mobile mass composed chiefly of muscular 
tissue, and covered by mucous membrane, which occupies the floor of the mouth 
and forms the anterior wall of the oral pharynx (Fig. 639). 
Whilst the sense of taste resides chiefly in its modified epithelium, the tongue 
is also an important organ of speech, and, in addition, it assists in the mastication 
and deglutition of the food—functions which it is well fitted to perform, owing to 
its muscular nature and great mobility. In length it measures, when at rest, 
about three and a half inches, but both its length and width are constantly 
varying with every change in the condition of the organ, an increase in length 
being always accompanied by a diminution in width, and vice versa. 
In describing the tongue we distinguish the following parts: the body (corpus 
linguze), made up chiefly of striped muscle, and forming the mass of the organ ; the 
dorsum (Fig. 640), which looks towards the palate and pharynx, and is free in its 
whole extent; the base, the posterior wide end which is attached to the hyoid 
bone ; the apex or tip, the pointed and free anterior extremity ; the margin, which is 
free in its anterior half or more, ¢.e. in front of the attachment of the anterior palatine 
arch (Fig. 640). Finally, the unattached portion on the inferior aspect, seen when the 
apex is turned strongly upwards (Fig. 643), constitutes the inferior surface ; whilst 
the attached portion, fixed by muscles and mucous membrane to the hy oid bone 
and mandible, is known as the root. 
The dorsum of the tongue (dorsum linguz), when the organ is .at rest, is 
strongly arched from before backwards in its whole length (Fig. 639), the oreatest 
convexity corresponding to the attachment of the anterior palatine folds. When 
removed from the body the tongue, unless previously hardened in situ, loses its 
natural shape, and appears as a flat, elongated oval structure, which gives a very 
erroneous idea of its true form and connexions. 
Corresponding to its differently-directed portions, the dorsum is naturally 
divided into two areas—an anterior or oral part, which lies nearly horizontally on 
the floor of the mouth, and constitutes about two-thirds of the length of the whole 
tongue (Fig. 640); and a posterior or pharyngeal part, the remaining third of 
the organ, which is placed nearly vertically, and forms the anterior wall of the 
oral pharynx (Fig. 641). The separation between these two parts, which differ 
in appearance as well as in direction, is indicated by a distinct V-shaped groove, — 
called the sulcus terminalis (Fig. 641), the apex of which is directed backwards, and j 
corresponds to a blind depression on the surface of the tongue, the foramen cecum, 
whilst its diverging limbs pass outwards and forwards towards the attachments of - 
