TEE TONGUE. 139 



pit forms a lodging-place for bits of food, which, in de- 

 composing, form acids and hasten the corrosion. Small 

 eroded cavities are very apt to be overlooked ; the teeth 

 should, therefore, be thoroughly examined two or three 

 times a year by a dentist. 



The Tongue (Fig. 46) is a muscular and highly mov- 

 able organ, covered by mucous membrane, and endowed not 

 only with a delicate sense of touch, but with the sense of 

 taste. Its root is attached to the hyoid bone (p. 26). 

 The mucous membrane covering the upper surface of the 

 tongue is roughened by numerous minute elevations or 

 papillae, of which there are three varieties. The circum- 

 vallate papillce (Fig. 46, 1 and 2) are the largest and fewest, 

 and lie near the root of the tongue, arranged in the form 

 of a V, with its open angle turned towards the lips. The 

 fungiform papillce are rounded masses attached by nar- 

 rower stems. They are found all over the middle and fore 

 part of the upper surface of the tongue, and during life 

 are readily recognized as red dots, more deeply colored 

 than the rest of the mucous membrane. The filiform 

 papillce are pointed elevations scattered all over the upper 

 surface of the tongue, except near its root. They are on 

 our tongues the smallest and most numerous.* 



Why is decay of a tooth apt to go on fast once it has commenced? 

 Why should the teeth be examined from time to time by a dentist? 



Briefly describe the tongue. What sensations do we obtain 

 through it? To what is its root attached? What are found on the 

 mucous membrane of the upper surface of the tongue? Of how 

 many varieties? Which are largest and fewest? Where are they 

 found? How are they arranged? Describe the fungiform papillae. 

 Where are they found? What do they look like when we examine 

 a person's tongue? Where are the filiform papillae found? What 

 is their form? What papillae on the human tongue are smallest? 

 Most numerous? 



* The filiform papillae are very large on the tongue of the cat, where they 

 may readily be seen and felt. They are large in nearly all carnivorous animals, 



