164 ELEMENTS OF PHYSIOLOGY 



the air takes in passing through the nose instead of the 

 mouth, nasal breathing brings the air in contact with a 

 much larger extent of moist and warm mucous membrane 

 than does mouth breathing. The air becomes warm and does 

 not, like cold air, irritate the trachea and bronchial tubes. 

 (2) The air becomes purified, because the hairs just within 

 the nostrils and the mucous lining of the latter serve to 

 catch particles of dust, and the mucus has the power of 

 destroying germs. (3) While a mouth breather is eating, 

 sufficient time is not taken for chewing the food, but it is 

 swallowed too soon, so urgent is the necessity for breathing. 

 (4) In the habitual mouth breather, 

 the nasal mucous membrane, from lack 

 of stimulus of the cold air, dries and 

 shrinks, causing discomfort ; and since, 

 in its dry condition, the circulation 

 easily becomes obstructed, there is a pre- 

 disposition to congestion and catarrhal 

 nasal affections and injury to hearing. 

 FIG. 142. -The Facial EX- ( 5 ) An unpleasant expression of the 



pression when breathing . 



through the Nose and f ace results from mouth breathing (Fig. 

 when breathing through I4 2) the lower jaw recedes, the upper 



the Mouth. J 



teeth project, the nostrils are not devel- 

 oped and in a grown man may be no larger than during 

 childhood. (6) A person has greater endurance in mus- 

 cular exertion if he breathes strictly through the nose. 

 He can hold out much longer, his lungs are kept more 

 expanded, and the heart is not oppressed ; and, after 

 a while, a "second wind" comes to him, for instance, 

 during running. (7) The voice has more resonance if the 

 nasal passages are open. 



A Scotch physician, fully appreciating the importance of 

 proper breathing, has written a valuable medical paper, 

 entitled, " Shut your Mouth and Save your Life." Some- 

 times the cause of stopping up the nose in children is 



