ORGANS OF DIGESTION. 



119 



cc 



cd 



a tonsil. In man, the tonsils sometimes become in- 

 flamed and enlarged, giving 

 rise to a disease called tonsil- 

 litis. The tonsil is a compound 

 lymphatic gland whose func- 

 tion is unknown. 



Folds of mucous membrane 

 called f rena bind the lips to the 

 gums, which are composed of 

 dense fibrous tissue investing 

 the alveolar margins of the 

 jaw-bones. The mucous lining 

 of the mouth contains many 

 simple mucous glands invisi- 

 ble to the naked eye. Those 

 of the lips are called labial, of 

 the cheeks, buccal, and of the 

 palate, palatine glands. 



The tongue lying in the floor 

 of the mouth is a muscular 

 mass composed of the genio- 

 hyoglossus, lingualis superfici- 

 alis superior and inferior, sty- 

 loglossus, and hyoglossus mus- 

 cles. Caudally it is attached 

 to the hyoid bone. Its invest- 

 ment of mucous membrane is 

 formed into a fold beneath it, 

 called the frenum linguae. The 

 dorsal surface of the tongue 

 displays four kinds of papillae 



FIG. 55. DORSAL ASPECT OF 

 THE TONGUE AND LARYNX. 



at, Arytenoid cartilage; a/, an- 

 terior pillar of the fauces ; cc, 

 crico-epiglottic ligament; cd, 

 true vocal cords; cv, circum- 

 vallate papilla; ep, epiglottis; 

 fl, flat papilla; fg, fungiform 

 papilla ; fr, filiform papilla ; gl, 

 glottis; hy, epihyal bone cut 

 off ; i, false vocal cord ; oe, lu- 

 men of the esophagus, which 

 is cut off just as it opens into 

 the pharynx ; pf, posterior pil- 

 lar of the fauces; tn, tonsil. 



(Fig. 55): The circumvallate, 



numbering from six to eight arranged in a V shape near 



the root; the flat, very numerous at the root; the conical, 



