558 



HANDBOOK OF PHYSIOLOGY. 



The surface of each kind is studded by minute conical processes of 

 mucous membrane, which thus form secondary papillae. 



Simple papillae also occur over most other parts of the tongue 

 not occupied by the compound papillae, and extend for some distance 

 behind the papillae circumvallatae. They are commonly buried beneath 

 the epithelium; hence they are often overlooked. The mucous mem- 

 brane immediately in front of the epiglottis is, however, free from them. 



Fia. 369. Papillar surface of the tongue, with the fauces and tonsils. 1, 1, circumvallate 

 papillae, in front of 2, the foramen caecum; 3, fungiform papillae; 4, filiform and conical papillse; 

 5, transverse and oblique rugas; 6, mucous glands at the base of the tongue and in the fauces; 7, 

 tonsils; 8, part of the epiglottis; 9, median glosso-epiglottidean fold (fraenum epiglottidis). (From 

 Sappey.) 



(1.) Circumvallate. These papillae (Fig. 370), eight or ten in num- 

 ber, are situate in two V-shaped lines at the base of the tongue (1, 1, 

 Fig. 369). They are circular elevations from -g^th to T Vth of an inch 

 wide, each with a central depression, and surrounded by a circular fissure, 

 at the outside of which again is a slightly elevated ring, both the central 



