Life and Health 



A 



' 156. The Pharynx. The pharynx forms a sac, into 

 which the mouth opens. Just above the mouth are the 

 two posterior passages into the nose. There are also little 

 openings, one on each side, from which 

 begin the Eustachian tubes, which lead 

 upward to the cavities in the interior 

 of the ear. 



The windpipe opens downward from 

 the pharynx, but this communication 

 can be shut off by a little plate or 

 lid of cartilage, the epiglottis. During 

 the act of swallowing this closes down 

 over the entrance to the windpipe, and 

 the windpipe rises up to meet the lid. 

 This prevents the food from passing 

 into the air passages (Figs. 45 and 5 i). 



Experiment 43. Open the mouth wide ; 

 press down the back of the tongue gently 

 with the handle of a teaspoon. With the 

 aid of strong sunlight and a hand mirror the 

 epiglottis may be seen. 



< 157. The (Esophagus. The oesopha- 

 gus, or gullet, is a tube about nine 

 inches long, reaching from the throat 

 to the stomach. It lies behind the windpipe, pierces the 

 diaphragm, which is between the chest and the abdomen, 

 and opens into the stomach. It has in its walls muscular 

 fibers, which, by their wave-like contractions, grasp the 

 successive masses of food as they pass downwards and 

 force them into the stomach. 



158. Deglutition, or Swallowing. The food, having been 

 well chewed and mixed with saliva, is now a soft, pasty 

 mass, ready to be swallowed. The tongue gathers it up and 



B 



c 



- D 



FIG. 48. Longitudinal 

 Section of a Tooth. 



A, enamel ; B, pulp cavity ; 

 C, dentine ; >, cement. 



