THE NOURISHMENT OF THE BODY 257 



up through the roots to the sensitive pulp within. When, 

 through decay, the pulp or nerve is exposed, toothache is the 

 result. To preserve the teeth, they should be brushed at 

 least once daily with a good stiff brush in order to remove 

 particles of food which otherwise would cause them to decay. 

 If the teeth are not cleaned after every meal, the best time to 

 brush them is after the evening meal. When the teeth begin 

 to decay, the dentist should be visited before the trouble has 

 proceeded far enough to cause the tooth to ache. The tooth 

 can then be treated without pain. It is a good plan to have 

 the teeth inspected by a dentist at least twice a year in order 

 that any beginning decay may be noticed in time. 



Practical Exercises 



1. How do clothes and shelter enable us to economize food? 



2. Why may bad news cause us to lose our appetite? 



3. Pick out the chief food constituents in the following food combina- 

 tions : bread and butter, mush and milk, pork and beans, pancakes and 

 sausage, macaroni and cheese, roast pork and apple-sauce, roast beef 

 and mashed potatoes. 



4. Chew a crust of bread for a long time and explain the sweet taste 

 that develops. 



5. Why may the sight of a person eating a lemon cause the mouth to 

 water? 



6. With a dull knife, scrape some cells from the inside of the cheek and 

 examine with the microscope. What is their shape? Locate the 

 nucleus. 



7. Which of the milk teeth are first to appear? 



17 



