The organs of respiration have their own protective apparatus... filter... or dust-catcher... in the nostrils. When the breath is taken through the mouth... there is nothing from mouth to lungs to strain the air... or to catch the dust and other foreign matter in the air. From mouth to lungs the dirt or impure substance has a clear track... and the entire respiratory system is unprotected. And... moreover... such incorrect breathing admits cold air to the organs... thereby injuring them. Inflammation of the respiratory organs often results from the inhalation of cold air through the mouth. A man who breathes through the mouth at night... always awakens with a parched feeling in the mouth and a dryness in the throat. He is violating one of nature's laws... and is sowing the seeds of disease.
Once more... remember that the mouth affords no protection to the respiratory organs... and cold air... dust and impurities and germs readily enter by that door. On the other hand... the nostrils and nasal passages show evidence of the careful design of nature in this respect. The nostrils are two narrow... tortuous channels... containing numerous bristly hairs which serve the purpose of a filter or sieve to strain the air of it's impurities... etc... which are expelled when the breath is exhaled. Not only do the nostrils serve this important purpose... but they also perform an important function in warming the air inhaled. The long narrow winding nostrils are filled with warm mucous membrane... which coming in contact with the inhaled air warms it so that it can do no damage to the delicate organs of the throat... or to the lungs.