Every cell in the body needs oxygen, and deprived of it will die, just as a candle flame will go out when the proportion of oxygen in the air falls below a certain level.
To ensure that each cell throughout the body receives its proper supply, we are fitted out with a delicate and a perfectly adjusted apparatus consisting of the air passage and lungs, and the heart and blood-vessels. Anything which interferes with the working of this apparatus impairs the supply of oxygen to the tissues and results in loss of vitality, ranging from the lassitude and weariness of an ordinary head cold to the extreme breathlessness and collapse of severe pneumonia.
Thus blocking of the nose by catarrh, or of the great air-tubes by bronchitis, bring about discomfort and breathlessness or exertion. In inflammation of the lungs such as occurs in pneumonia, part of the lung substance is “knocked out,” and blueness and rapid breathing results. The heart has to beat more rapidly to try to make up for the poor oxygen supply, and is liable to become overstrained in consequence.
The importance of correct nasal hygiene has been stressed by all surgeons and Yogis. When the air is drawn in during inspiration, it passes along the upper part of the nose, near the “roof”. Expired air passes out along the floor. The best way, therefore, to clear the nose of mucous with entangled germs and debris is to breathe in deeply through the nose, with the mouth closed, sniffing slightly, thus allowing deleterious material to collect on the floor of the organ, then breathe out forcibly, holding one nostril shut. Dust, germs and debris should first have been cleaned out of the entrance to the nostrils by the warm ‘Jala-neti‘.
The defensive mechanism of the nose is powerlesss to protect the body against the evil effects of constantly inhaled irritant dusts. Adenoids are said to be more common in dusty regions. Hence the ‘Jala-neti’ (warm or cold according to the nature of the ‘sadhaka’) should be regularly done.
Except in circumstances of constant exposure to dust the defensive mechanism of the nose Is very efficient and, by the time the inhaled air reaches the throat, it is normally, practically free from germs. In the throat it encounters the tonsils, which when healthy, act as accessory germ traps.** If, however, the lining of the nose or the tonsils become inflamed by a cold, their protective function fails and the body is more prone to infection by the germs or more serious diseases.