I io HUMAN PHYSIOLOGY CHAP. 



lukewarm water should be used at least twice a day, or, 

 still better, after each meal and just before going to bed 

 at night. Besides, it may be well to clean each tooth 

 occasionally with a chisel-like piece of hard wood. This 

 gives the teeth a smooth polish, and makes it easier to 

 clean them with a brush. About twice a year they should 

 be looked over by a dentist and repaired if they need it. 



87. The Appetite. A person who lives as he should 

 may safely trust his appetite as to what he shall eat. 

 In this matter the lower animals have no trouble, but 

 man is always concocting something new to give greater 

 variety to his diet, and so stimulate his natural desire 

 for food. This leads to disturbances of various sorts. 

 How many things that a person dislikes at first he learns 

 to eat by repeated attempts. In this way an artificial 

 appetite may be created for any new thing whether 

 wholesome or injurious. 



The condition of the mind and nervous system has 

 a wonderful influence upon the appetite as well as upon 

 digestion and nutrition. A cheerful disposition and a 

 joyous nature give rise to good digestion and more 

 perfect nutrition, while worry, envy, jealousy, excite- 

 ment, and other undesirable states of mind lead to 

 digestive disturbances that make good health an 

 impossibility even when a person takes the best of 

 care of himself. A pure-minded, cheerful, contented, 

 industrious person is likely to have a good appetite and 

 good digestion. We can now understand the phrase, 

 " laugh and grow fat," and see why a change of scene 

 and a long vacation are often the best of medicines. 



