150 



ELEMENTARY BIOLOGY 



is an unconscious and an involuntary process. The way you 

 breathe is entirely a matter of habit and surroundings. 



181. Nose-breathing and mouth-breathing. Normal breath- 

 ing carries the air out as well as in through the nose, not 

 the mouth. We should acquire the habit of breathing through 



the nose rather than 

 through the mouth, for 

 the following reasons : 



1 . The lining of the 

 nose secretes a layer of 

 mucus, in which fine 

 particles of dust are 

 caught before getting 

 to the windpipe. 



2. Coarser particles 

 are filtered out by the 

 hairs that line the front 

 nostrils. 



3. The long, narrow 

 nose passages warm 

 the incoming air before 

 it reaches the more deli- 

 cate lining of the air 

 pipes of the lungs. 



This habit should be 

 formed early in life ; 

 most people are incap- 

 able of getting new 

 habits or breaking old habits after they grow to maturity. 

 Watch yourself, and when you catch yourself breathing through 

 the mouth, make up your mind to stop the trick, and have 

 your closest friend or relations help you by reminding you 

 when you forget yourself. 



Breathing through the mouth is objectionable on two other 

 grounds besides the hygienic ones : 



FlG. 49. 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) 



