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Rh through the mouth. There are, however, very few persons who know how to breathe correctly. Many people are in the pernicious habit of inhaling through the mouth. If very cold air is inhaled through the mouth, we catch cold and sore throat. Further, if we inhale through the mouth, the particles of dust in the air go into the lungs and cause great mischief. In London, for instance, in November, the smoke which issues from the chimnies of great factories mixes with the dense fog, producing a kind of yellew mixture. This contains tiny particles of soot, which can be detected in the spittle of a man who inhales through the mouth. To escape this, many women (who have not learnt to breathe through the nose alone) put on a special kind of veil over their faces, which act as sieves. If these veils are closely examined, particles of dust can be detected in them. But God has given to all of us a sieve of this kind inside the nose. The air which is inhaled through the nostrils is sifted before it reaches the lungs, and is also warmed in the process. So all men should learn to breathe through the nose alone. And this is not at all difficult, if we remember to keep our mouth firmly shut at all times, except when we are talking. Those who have got into the habit of keeping their mouth open should sleep with a bandage round the mouth,