THE TONGUE 



1221 



ward and forward just in front of the sulcus terminalis. These papillae are partially or wholly 

 submerged, that is, lie in depressions. Each consists of a narrow base, attached at the bottom 

 of the depression, while the remainder is surrounded by the vallum or ditch. Each papilla is 

 from 2<r to j2 inch in width and possesses secondary papillae. In the epithelium of the sides 

 are found the taste buds. 



The foramen cecum, according to His, represents the remains of the evagination that formed 

 the middle lobe of the thyroid body and the upper end of the supposed thyroglossal duct (ductus 

 thyroylossus). This may exist as a canal, at times extending toward the hyoid bone. 



Filiform. 



FuiHjiform. 



Secondary 

 papillse. 



(Srcumvattate. 



Artery. 



A tiery.' 

 Vein. 



FIG. 939. Three kinds of papillae, magnified. 



Upon the posterior or basal one-third of the dorsum of the tongue papilla? are not found. 

 The surface is irregular, however, due to the presence of follicular collections of lymphoid tissue, 

 that produce rounded elevations of the mucosa. Each follicle possesses a little pit or crypt, and 

 collectively the follicles are termed the lingual tonsil (tonsilla lingualis}. Each crypt is lined 

 by stratified squamous epithelial cells upon basement membrane and tunica propria ; in the latter 

 are numerous solitary follicles arranged around the pit, and each group is isolated from the 

 neighboring collection. 



Beneath the tunica propria of the mucosa is the 

 muscle tissue of the tongue. This muscle tissue 

 is of the voluntary striated variety and is divided 

 into two sets of muscles Intrinsic and Extrinsic 

 (described on p. 395). 



Scattered throughout the tongue, but especially 

 located in definite areas, are glands of a mucous 

 and serous character. The mucous glands are 

 found behind the circumvallate papillae and along 

 the margins, and an especial group at the apex, 

 called the apical glands or glands of Nuhn and 

 Blandin (glandiilae linguales anteriores of Nuhn 

 and Blandin) (Fig. 941). Each gland is situated 

 at the side of the frenulum and is covered by a 

 fasciculus of muscle fibres derived from the Stylo- 

 glossus and Inferior lingualis muscles. Each gland 

 is from one-half inch to nearly an inch in length 

 (1 to 2 cm.) and about one-third of an inch broad 

 (8 mm.). Each gland has from four to six ducts, 

 which open on the under surface of the apex. 

 The serous glands, or glands of von Ebner, occur 

 in the basal part of the tongue, the ducts opening 

 chiefly into the fossae around the circumvallate 

 papillae. Both mucous and serous glands resemble 

 the other salivary glands in structure (p. 1228). 



The Vessels of the Tongue. The arteries of the tongue are derived from the lingual, the 

 facial, and ascending pharyngeal. The veins of the tongue open into the internal jugular. 



The lingual artery (Fig. 943) on each side passes forward beneath the Hyoglossus muscle 

 and courses to the apex of the tongue, between the Genioglossus and the Inferior lingual muscles, 

 about one-eighth of an inch from the surface. It divides into the ranine (Fig. 941) and sub- 

 lingual (Fig. 943). Near the apex a branch is given off from the ranine artery, which pene- 



Fio. 940. Circumvallate papillse of tongue of 

 rabbit, showing position of taste goblets, a. 

 Duct of gland, d. Serous gland, (i. Taste buds. 

 /. Primary septa, and /', secondary septa, of 

 papillae, n. Myelinated nerve. M. Muscle fibres. 

 (Stohr.) 



