ADVANCED PHYSIOLOGY 



tells one that he is not treating his teeth properly since a tooth- 

 ache generally means decay. If one avoids injuring the en- 

 amel with hard substances, and if he does not allow food to 

 remain between the teeth for the bacteria to act upon, he can 

 thus check the pro-cess of decay. Carbohydrate foods are most 

 liable to be turned acid by bacteria, and hence bits of cracker 

 or bread are among the worst materials to leave lodged in 

 the mouth. 



When a tooth begins to decay, the dentist removes the 

 decaying portion; he then closes the opening with gold or 

 silver or some other hard material. It is extremely important 

 to have a cavity attended to when it is very small so as to 



save the tooth; hence the 



Papi/toeivithtostebuds 



teeth snou i d be examined 

 by a dentist at least twice 

 a year. This is not only 

 necessary as a means to uni- 

 form health, but, contrary to 

 the belief of some, is much 

 the most economical custom 

 for every one. 



The Tongue. The tongue 

 is a mass of muscles whose 

 fibres can move it in differ- 

 ent ways, either guiding 

 the food in the process 

 of chewing or carrying 

 the food back toward the 

 gullet. On the upper surfaces of this organ are numer- 

 ous minute projections, or papillge; Fig. 38. Everyone has 

 noticed the very rough tongues of dogs and cats. On the hu- 

 man tongue are three kinds of papillse. The largest, called 

 the circumvallate, are few in number and at the very back of 

 the tongue; Fig. 38. These papilla? are short and blunt in 



FIG. 38. THE SURFACE OP THE 

 TONGUE 



