164 



BIOLOGY AND HUMAN LIFE 



b. The long, narrow nose passages warm the air before it 

 reaches the more delicate lining of the air pipes of the lungs. 



c. The appearance of a mouth breather is unattractive. 



d. Mouth breathing leads to snoring, which is due to the 

 vibration of the soft palate by a current of air coming from 



the pharynx through 

 the nose. 



People do not snore 

 while awake ; during sleep 

 the muscles of the mouth 

 and the palate relax, and 

 the moving air sets up a 

 vibration of the hind 

 palate. A frequent cause 

 of mouth breathing is 

 some obstruction in the 

 nasal passage. The most 

 common obstruction is 

 an outgrowth of the lin- 

 ing in the hind nostrils, 

 called an adenoid growth 

 (see Fig. 87). Such a 

 growth is a handicap to a 

 child, since it interferes 

 with proper breathing and 

 sometimes with the cir- 

 culation of blood in the 

 head. 



2. Deep breathing. 

 Some of the air sacs 



Fig. 86. Expression of face associated 

 with adenoids 



The open mouth, the sleepy eyes, the strain about 



the nose, are results of defective breathing due to 



obstructions in the rear air passages of the nose, 



(From a photograph by Jessie Tarbox Beals) 



of the lungs (especially 

 those in the upper corners) can be ventilated only by forced 

 breathing ; and it is in these very parts that tuberculosis of the 

 lungs most frequently begins. It is desirable that all the air 

 sacs be completely filled from time to time. Vigorous exercise 

 of the large muscles of the arms and legs and trunk will auto- 

 matically force deeper breathing. Those of us whose occupa- 



