126 RESPIRATION. 



box of cartilage, across which are stretched the vocal cords. 

 Here the voice is produced chiefly by the passage of the 

 respired air over these cords, causing them to vibrate. 



FIG. 37. SECTION OF THE LUNGS. 



5. Over the opening of the larynx is found the epiglottis, 

 which fits like the lid of a box at the entrance to the 

 lungs, and closes during the act of swallowing, so that 

 food and drink shall pass backward to the oesophagus, or 

 gullet (Fig. 38). Occasionally it does not close in time, 

 and some substance intrudes within the larynx, when we at 

 once discover, by a choking sensation, that "something has 

 gone the wrong way," and, by coughing, we attempt to ex- 

 pel the unwelcome intruder. The epiglottis is one of the 

 many safeguards furnished by nature for our security and 



5. The epiglottis ? When it does not close in time, what is the consequence? 



