THE RESPIRATION 



149 



into which both the mouth and nasal passages open, is 

 called \h.Q pharynx (far 1 inks), or throat. Below, two tubes 

 open from the pharynx, one into the trachea (trdk'e-a) 

 or windpipe, the other into the esophagus, or gullet. At 

 the top of the trachea 

 (Fig. 129)13 the carti- 

 laginous larynx, or 

 voice box, and the 

 opening from the 

 throat is provided 

 with a lid, the epi- 

 glottis, also consisting 

 of cartilage. The lar- 

 ynx will be described 

 more fully in treating 

 of the voice ; it may 

 be felt as the Adam's 

 apple. Just below it 

 comes the trachea 

 proper which is a tube 

 about three fourths of FIG. 128. 



an inch in diameter, I; l argest cartilage of larynx; , lowest cartilage of 



and about four inches %&*"* the divisions and subdivision$ 

 long (Fig. 129). It 



consists of hoops of cartilage which are not complete 

 circles but are shaped somewhat like the letter C, being 

 completed behind by nonstriated (involuntary) muscular 

 tissue (Fig. 130), whose function is to draw the ends 

 of the rings together at times, e.g. during coughing, 

 and reduce the caliber of the tube. The function of 

 the hoops of cartilage is to keep the windpipe open 

 at all times. If it should collapse under pressure, life 

 might be lost. These rings of cartilage may be felt in 

 the neck. 



250. The lower end of the trachea is just behind the 



