16 PHYSIOLOGY AND HEALTH. 



leads forward to the mouth, the second upward and forward 

 to the nose, the third downward to the windpipe and lungs, 

 and the fourth downward and backward to the stomach. 

 The (esophagus, or gullet, that carries the food and drink to 

 the stomach, opens from the farthest part of the mouth, and 

 lies behind the windpipe, next to the back-bone. 



20. The windpipe opens between the tongue and the gullet, 

 in the front part of the throat. It is seen and felt in all per- 

 sons, and in some it is very prominent. As the windpipe 

 lies between the tongue and the gullet, the food, going from 

 the mouth to the stomach, must pass over it, and would be 

 liable to fall in if there were not an effectual protection pro- 

 vided against this accident. The windpipe is made of a 

 number of stiff cartilages, and its mouth is always open; 

 but there is placed over this mouth a little clapper, or valve, 

 called the epiglottis, which is fixed by a hinge to the front 

 edge toward the tongue, and opens toward the O3sophagus 

 behind. 



21. This valve usually stands open to allow the passage of 

 air into and out of the lungs. But it is exquisitely sensitive ; 

 when it is touched with any other matter, it falls down at 

 once, and covers the aperture of the windpipe, and protects 

 it from any intrusion. Whenever we swallow food or drink, 

 the instant the morsel or the fluid reaches this valve, it falls, 

 and allows it to glide over it, into the gullet behind, and then 

 it rises again to give passage to the air. 



22. While we are swallowing we cannot breathe ; if we 

 attempt to do this, or to speak, or do any thing which will 

 cause this valve to open, some minute particle of food or 

 drop of fluid may get into the windpipe, and cause painful 

 irritation and coughing. This is a common accident, and 

 may be easily prevented by not speaking while attempting to 

 swallow food or drink. At the same time that the epiglottis 

 falls to allow the food to pass safely over the windpipe, the 

 soft palate, the curtain that hangs between the front and the 

 back chamber of the mouth, is turned backward and up- 

 ward, and covers the passage-way that leads to the nostrils, 

 and defends them from the ingress of the food. 



