THE ALIMENTARY CANAL 



227 



tongue is held to the floor of the mouth by the fold known as 



the frenulum linguae. The frenulum contains parts of the two 



genioglossus muscles, which enter the tongue through it. The 



ventral surface and lateral borders of the tongue are smooth, 



soft, and free from papillae. The 



dorsal surface is raised into papillae 



of various kinds, and has a slight 



median longitudinal furrow. The 



caudal part of the dorsal surface is 



softer, redder, and marked with 



papillae of a different kind from 



those of the rest of the tongue. 



From the caudal end a small 



median vertical fold, the frenulum 



(or plica) glossoepiglottica passes 



from the dorsal surface of the 



tongue to the cranial surface of the 



epiglottis. 



The papillae of the tongue are 

 of three kinds. I. The very num- 

 erous filiform papillae (a) (pap- 

 illae filiformes) ; many of them 

 are horny and tooth-like, with 

 points turned caudad. These are 

 most numerous at the middle of 

 the free end of the tongue. 2. The 

 fungiform papillae (b] (papillae 

 fungiformes) are found scattered 



over the surface of the middle of FIG. 95. TONGUE, EPIGLOTTIS, 

 the tongue caudad of the large AND PENING OF LAR X. 



,.,... .,, a, filiform papillae; 6, fungiform 



filiform papillae. They are en- papilla; f, very large papillae at the 



larged at their free ends. There side .^ , of t] ? e ton &ue; '. circumvallate 



papillae; a, tonsils; e, epiglottis; /, 



is a prominent row of very large plica aryepiglottica; g, arytenoid car- 

 ones (b'} opposite the circumval- ^ s ( c< 7, red wit , h cosa ); *, 



glottis; t, false vocal cords; j, true 



late papillae at the borders of the vocal cords, 

 tongue. 3. The circumvallate papillae (c) (papillae vallatae) 

 are blunt and each is surrounded by a trench which is bounded 

 in turn by a raised wall. They are in two rows of two or three 



