1126 



SPLANCHNOLOGY 



smoother, and contains numerous muciparous glands and lymph follicles (lingual 

 tonsil). The foramen cecum is the remains of the upper part of the thyroglossal 

 duct or diverticulum from which the thyroid gland is developed; the pyramidal 

 lobe of the thyroid gland indicates the position of the lower part of the duct. 



The Papillae of the Tongue (Fig. 1014) are projections of the corium. They are 

 thickly distributed over the anterior two-thirds of its dorsum, giving to this surface 

 its characteristic roughness. The varieties of papilla? met with are the papillae 

 vallatae, papillae fungiformes, papillae filiformes, and papillae simplices. 



Anterior lingual gland 



Lingual nerve 



Art. pro/undo, linguae t 



Vena com, n. hypoglossi 



JJongitudinalis inferior 



Plica fimbriata, 



Vena com*, n hypoglossi 



Frenulum 



Orifice of submax. duct 

 lica sublingualis 



FIG. 1013. The mouth cavity. The apex of the tongue is turned upward, and on the right side a superficial 

 dissection of its under surface has been made. 



The papillae vallatae (circumvallate papillae) (Fig. 1015) are of large size, and vary 

 from eight to twelve in number. They are situated on the dorsum of the tongue 

 immediately in front of the foramen cecum and sulcus terminalis, forming a row 

 on either side; the two rows run backward and medial ward, and meet in the middle 

 line, like the limbs of the letter V inverted. Each papilla consists of a projection 

 of mucous membrane from 1 to 2 mm. wide, attached to the bottom of a circular 

 depression of the mucous membrane; the margin of the depression is elevated to 

 form a wall (vallum), and between this and the papilla is a circular sulcus termed 

 the fossa. The papilla is shaped like a truncated cone, the smaller end being 

 directed downward and attached to the tongue, the broader part or base projecting 

 a little above the surface of the tongue and being studded with numerous small 

 secondary papillae and covered by stratified squamous epithelium. 



The papillae fungiformes (fungiform papilla) (Fig. 1017), more numerous than the 

 preceding, are found chiefly at the sides and apex, but are scattered irregularly 

 and sparingly over the dorsum. They are easily recognized, among the other 



