302 DIGESTION AND ABSORPTION 



all, called premolars. Lastly, the flat-top molars, or grinding teetn, 

 of which there are six in each jaw. Food is caught between 

 irregular projections on the surface of the molars and crushed 

 to a pulpy mass. 



Hygiene of the Mouth. — Food should simply be chewed and rel- 

 ished, with no thought of swallowing. There should be no more ef- 

 fort to prevent than to force swallowing. It will be found that if you 

 attend only to the agreeable task of extracting the flavors of your 

 food, Nature will take care of the swallowing, and this will become, 

 like breathing, involuntary. The instinct by which most people 

 eat is perverted through the " hurr}^ habit " and the use of abnor- 

 mal foods. Thorough mastication takes time, and therefore one 

 must not feel hurried at meals if the best results are to be secured. 

 The stopping point for eating should be at the earliest moment after 

 one is really satisfied. 



Care of the Teeth. — It has been recently found that fruit acids 

 are very beneficial to the teeth. Vinegar diluted to about half 

 strength with water makes an excellent dental wash. Clean your 

 teeth carefully each morning and before going to bed. Use dental 

 silk after meals. We must remember that the bacteria which 

 cause decay of the teeth are washed down into the stomach and 

 may do even more harm there than in the mouth. 



How Food is Swallowed. — After food has been chewed and 

 mixed with saliva, it is rolled into little balls and pushed by the 

 tongue into such position that the muscles of the throat cavity 

 may seize it and force it downward. Food, in order to reach the 

 gullet from the mouth cavity, must pass over the opening into 

 the windpipe. When food is in the course of being swallowed, 

 the upper part of this tube forms a trapdoor over the opening. 

 When this trapdoor is not closed, and food " goes down the wrong 

 way," we choke, and the food is expelled by coughing. 



The Gullet, or Esophagus. — Like the rest of the food tube 

 the gullet is lined by soft and moist mucous membrane. The 

 wall is made up of two sets of muscles, — the inside ones running 

 around the tube ; the outer layer of muscle taking a longitudinal 

 course. After food leaves the mouth cavity, it gets beyond our 

 direct control, and the muscles of the gullet, stimulated to activity 



