436 SCIENCE OF HOME AND COMMUNITY 



remarkable cures of rheumatism have been effected by simply 

 cleaning the teeth. 



Purposes of mastication. Mastication serves many useful 

 purposes as we have already learned in Chapter V. These 

 uses may be briefly summarized as follows : first, mastica- 

 tion grinds the food into a fine mass and thus prepares it 

 for the process of digestion which takes place in the stomach 

 and intestines ; 'Second, the thorough mixture with the 

 saliva begins the act of digestion of the starch; third, 

 thorough mastication better enables one to determine how 

 much food and what kinds he should eat; fourth, it pro- 

 vides the necessary stimulus for the normal growth of the 

 teeth and jaw ; fifth, thorough mastication helps to clean 

 the teeth. When the teeth are defective, mastication is 

 done less thoroughly, and hence these purposes are ful- 

 filled less successfully. 



Dental clinics. Dental clinics are now being introduced 

 into many of our cities. The teeth of the children are ex- 

 amined and treated free by dentists hired by the school 

 authorities. As teachers are hired to teach children how 

 to read, so dentists are hired to look after the children's teeth. 

 These clinics are very common in Europe, and are rapidly 

 increasing in number in this country. Eventually these 

 clinics will doubtless be found in every city and town. 

 When a town is too small to afford it, several towns may 

 join together to hire a dentist. One agricultural paper sug- 

 gests that a new " R. F. D." be established, " rural free 

 'dentistry." 



Defects of the eye. About one quarter of all children are 

 suffering from defects of the eye. In order to understand 

 what these defects are, we shall need to examine the eye 

 to see how it is constructed and how it works. We may 

 compare it with a camera. The eyeball corresponds to the 

 camera box, the lens in the eye to the camera lens, the iris 

 and the pupil of the eye to the diaphragm of the camera, 



