

THE MOUTH 



The Verticalis linguae (Vertical lingualis) is found only at the borders of the fore- 

 part of the tongue. Its fibers extend from the upper to the under surface of the 

 organ. 



The median fibrous septum of the tongue is very complete, so that the anastomosis between 

 the two lingual arteries is not very free. 



Nerves. The muscles of the tongue described above are supplied by the hypoglossal nerve. 



Actions. The movements of the tongue, although numerous and complicated, may be under- 

 stood by carefully considering the direction of the fibers of its muscles. The Genioglossi, by means 

 of their posterior fibers, draw the root of the tongue forward, and protrude the apex from the 

 mouth. The anterior fibers draw the tongue back into the mouth. The two muscles acting in 

 their entirety draw the tongue downward, so as to make its superior surface concave from side 

 to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The 

 Hyoglossi depress the tongue, and draw down its sides. The Styloglossi draw the tongue upward 

 and backward. The Glossopalatini draw the root of the tongue upward. The intrinsic muscles 

 are mainly concerned in altering the shape of the tongue, whereby it becomes shortened, nar- 

 rowed, or curved in different directions; thus, the Longitudinalis superior and inferior tend to 

 shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render 

 the dorsum concave, while the latter pull the tip downward and render the dorsum convex. 

 The Transversus narrows and elongates the tongue, and the Verticalis flattens and broadens it. 

 The complex arrangement of the muscular fibers of the tongue, and the various directions in 

 which they run, give to this organ the power of assuming the forms necessary for the enuncia- 

 tion of the different consonantal sounds; and Macalister states "there is reason to believe that 

 the musculature of the tongue varies in different races owing to the hereditary practice and 

 habitual use of certain motions required for enunciating the several vernacular languages." 



Structure of the Tongue. The tongue is partly invested by mucous membrane and a sub- 

 mucous fibrous layer. 



The mucous membrane (tunica mucosa lingute) differs in different parts. That covering the 

 under surface of the organ is thin, smooth, and identical in structure with that lining the rest 

 of the oral cavity. The mucous membrane of the dorsum of the tongue behind the foramen 

 cecum and sulcus terminalis is thick and freely movable over the subjacent parts. It contains 

 a large number of lymphoid follicles, which together constitute what is sometimes termed the 

 lingual tonsil. Each follicle forms a rounded eminence, the center of which is perforated by a 

 minute orifice leading into a funnel-shaped cavity or recess; around this recess are grouped 

 numerous oval or rounded nodules of lymphoid tissue, each enveloped by a capsule derived from 

 the submucosa, while opening into the bottom of the recesses are also seen the ducts of mucous 

 glands. The mucous membrane on the anterior part of the dorsum of the tongue is thin, inti- 

 mately adherent to the muscular tissue, and presents numerous minute surface eminences, the 

 papillae of the tongue. It consists of a layer of connective tissue, the corium or mucosa, covered 

 with epithelium. 



The epithelium is of the stratified squamous variety, similar to but much thinner than that 

 of the skin: and each papilla has a separate investment from root to summit. The deepest cells 

 may sometimes be detached as a separate layer, corresponding to the rete mucosum, but they 

 never contain coloring matter. 



The corium consists of a dense felt-work of fibrous connective tissue, with numerous elastic 

 fibers, firmly connected with the fibrous tissue forming the septa between the muscular bundles 

 of the tongue. It contains the ramifications of the numerous vessels and nerves from which 

 the papillae are supplied, large plexuses of lymphatic vessels, and the glands of the tongue. 



Structure of the Papillae. The papillae apparently resemble in structure those of the cutis, 

 consisting of cone-shaped projections of connective tissue, covered with a thick layer of stratified 

 squamous epithelium, and containing one or more capillary loops among which nerves are dis- 

 tributed in great abundance. If the epithelium be removed, it will be found that they are not 

 simple elevations like the papillae of the skin, for the surface of each is studded with minute 

 conical processes which form secondary papillae. In the papillae vallataj, the nerves are numer- 

 ous and of large size; in the papillae fungiformes they are also numerous, and end in a plexiform 

 net-work, from which brush-like branches proceed; in the papillae filiformes, their mode of 

 termination is uncertain. 



Glands of the Tongue. The tongue is provided with mucous and serous glands. 



The mucous glands are similar in structure to the labial and buccal glands. They are found 

 especially at the back part behind the vallate papillae, but are also present at the apex and mar- 

 ginal parts. In this connection the anterior lingual glands (Blandin or Nuhn) require special 

 notice. They are situated on the under surface of the apex of the tongue (Fig. 1013), one on either 

 side of the frenulum, where they are covered by a fasciculus of muscular fibers derived from the 

 Styloglossus and Longitudinalis inferior. They are from 12 to 25 mm. long, and about 8 mm. 

 broad, and each opens by three or four ducts on the under surface of the apex. 



The serous glands occur only at the back of the tongue in the neighborhood of the taste-buds, 



