THE SKIN 19 



composed in the warm, moist mouth; (3) by the collection 

 of tartar on the teeth (Fig. 23). This is a deposit formed 

 because the secretion of the mouth is in improper condi- 

 tion. It affords an inviting soil in which germs may grow 

 and attack the teeth. (4) Constant nibbling of candy be- 

 tween meals is a bad habit, as the 

 sugar may ferment in the mouth and 

 change to an acid, which injures the 

 teeth. 



25. A toothbrush is more effective 

 when it is rubbed up and down as 

 well as across the teeth. A tooth- 



. . . FIG. 23. Human Teeth ; 

 pick IS as important as a toothbrush. sockets injured by tartar 



As a tooth powder, fine precipitated ( n left ) ; uninjured (on 

 chalk is best; it helps to clean the 



teeth and destroys sourness due to acids. Do you like 

 to leave the table with a sweet taste in the mouth ? 

 Why does chalk injure the skin, although good for the 

 teeth ? 



26. THOUGHT LESSON. The Complexion. i . Draw 

 lines under the words which name qualities belonging to 

 a healthy skin : hard, soft, dry, moist, flexible, elastic, 

 firm, flabby, smooth, dingy, rough, pink, yellow, pale, vel- 

 vety. 



2. The and the upon the skin keep it from 



being dry. 



3. These secretions come from the and the . 



4. The organs that furnish these secretions get their 

 material from the . 



5. What is the best means of improving the circulation 

 in the skin ? 



6. When a pore is so full of dirt and oil that you can 

 see it, what is it called ? 



7. You have considered what makes the skin soft; let 

 us think what will make it dry and hard. When our 



