# Hatha Yoga/Chapter 7

CHAPTER VII
THE CREMATORY OF THE SYSTEM
The Organs of Respiration consist of the lungs and the air passages leading to them. The lungs are two in number, and occupy the pleural chamber of the thorax, one on each side of the median line, being separated from each other by the heart, the greater blood-vessels and the larger air tubes. Each lung is free in all directions, except at the root, which consists chiefly of the bronchi, arteries and veins connecting the lungs with the trachea and heart. The lungs are spongy and porous, and their tissues are very elastic. They are covered with a delicately constructed but strong sac, known as the pleural sac, one wall of which closely adheres to the lung, and the other to the inner wall of the chest, and which secretes a fluid which allows the inner surfaces of the walls to glide easily upon each other in the act of breathing.
The Air Passages consist of the interior of the nose, pharynx, larynx, windpipe or trachea, and the bronchial tubes. When we breathe, we draw in the air through the nose, in which it is warmed by contact with the mucous membrane, which is richly supplied with blood, and after it has passed through the pharynx and larynx it passes into the trachea or windpipe, which subdivides into numerous tubes called the bronchial tubes (bronchia), which, in turn, subdivide into and terminate in minute subdivisions ​in all the small air spaces in the lungs, of which the lung's contain millions. A writer has stated that if the air cells of the lungs were spread out over an unbroken surface, they would cover an area of fourteen thousand square feet.
The air is drawn into the lungs by the action of the diaphragm, a great, strong, flat, sheet-like muscle, stretched across the chest, separating the chest-box from the abdomen. The diaphragm's action is almost as automatic as that of the heart, although it may be transformed into a semi-voluntary muscle by an effort of the will. When it expands, it increases the size of the chest and lungs, and the air rushes into the vacuum thus created. When it relaxes the chest and lungs contract and the air is expelled from the lungs.
Now, before considering what happens to the air in the lungs, let us look a little into the matter of the circulation of the blood. The blood, as you know, is driven by the heart, through the arteries, into the capillaries, thus reaching every part of the body, which it vitalizes, nourishes and strengthens. It then returns by means of the capillaries by another route, the veins, to the heart, from whence it is drawn to the lungs.
The blood starts on its arterial journey, bright red and rich, laden with life-giving qualities and properties. It returns by the venous route, poor, blue and dull, being laden down with the waste matter of the system. It goes out like a fresh stream from the mountains; it returns as a stream of sewer water. This foul stream goes to the right auricle of the heart. When this auricle becomes filled, it contracts and ​forces the stream of blood through an opening in the right ventricle of the heart, which in turn sends it on to the lungs, where it is distributed by millions of hair-like blood vessels to the air cells of the lungs, of which we have spoken. Now, let us take up the story of the lungs at this point.
The foul stream of blood is now distributed among the millions of tiny air cells in the lungs. A breath of air is inhaled and the oxygen of the air comes in contact with the impure blood through the thin walls of the hair-like blood vessels of the lungs, which walls are thick enough to hold the blood, but thin enough to admit the oxygen to penetrate them. When the oxygen comes in contact with the blood, a form of combustion takes place, and the blood takes up oxygen and releases carbonic acid gas generated from the waste products and poisonous matter which has been gathered up by the blood from all parts of the system. The blood thus purified and oxygenated is carried back to the heart, again rich, red and bright, and laden with life-giving properties and qualities. Upon reaching the left auricle of the heart, it is forced into the left ventricle, from whence it is again forced out through the arteries on its mission of life to all parts of the system. It is estimated that in a single day of twenty-four hours, 35,000 pints of blood traverse the capillaries of the lungs, the blood corpuscles passing in single file and being exposed to the oxygen of the air on both of their surfaces. When one considers the minute details of the process alluded to, he is lost in wonder and admiration at Nature's infinite care and intelligence.
It will be seen that unless fresh air in sufficient ​quantities reaches the lungs, the foul stream of venous blood cannot be purified, and consequently not only is the body thus robbed of nourishment, but the waste products which should have been destroyed are returned to the circulation and poison the system, and death ensues. Impure air acts in the same way, only in a lessened degree. It will also be seen that if one does not breathe in a sufficient quantity of air, the work of the blood cannot go on properly, and the result is that the body is insufficiently nourished and disease ensues, or a state of imperfect health is experienced. The blood of one who breathes improperly is, of course, of a bluish, dark color, lacking the rich redness of pure arterial blood. This often shows itself in a poor complexion. Proper breathing, and a consequent good circulation, results in a clear, bright complexion.
A little reflection will show the vital importance of Correct breathing. If the blood is not fully purified by the regenerative process of the lungs, it returns to the arteries in an abnormal state, insufficiently purified and imperfectly cleansed of the impurities which it took up on its return journey. These impurities if returned to the system will certainly manifest in some form of disease, either in a form of blood disease or some disease resulting from impaired functioning of some insufficiently nourished organ or tissue.
The blood, when properly exposed to the air in the lungs, not only has its impurities consumed, and parts with its noxious carbonic acid gas, but it also takes up and absorbs a certain quantity of oxygen which it carries to all parts of the body, where it is ​needed in order that Nature may perform her processes properly. When the oxygen comes in contact with the blood, it unites with the hæmoglobin of the blood and is carried to every cell, tissue, muscle and organ, which it invigorates and strengthens, replacing the worn-out cells and tissue by new materials which Nature converts to her use. Arterial blood, properly exposed to the air, contains about 25 per cent of free oxygen.
Not only is every part vitalized by the oxygen, but the act of digestion depends materially upon a certain amount of oxygenation of the food, and this is only accomplished by the oxygen in the blood coming in contact with the food and producing a certain form of combustion. It is therefore necessary that a proper supply of oxygen be taken through the lungs. This accounts for the fact that weak lungs and poor digestion are so often found together. To grasp the full significance of this statement, one must remember that the entire body receives nourishment from the food assimilated, and that imperfect assimilation always means an imperfectly nourished body. Even the lungs themselves depend upon the same source for nourishment, and if through imperfect breathing the assimilation becomes imperfect, and the lungs in turn become weakened, they are rendered still less able to perform their work properly, and so in turn the body becomes further weakened. Every particle of food and drink must be oxygenated before it can yield us the proper nourishment, and before the waste products of the system can be reduced to the proper condition to be eliminated from the system. Lack of sufficient ​oxygen means imperfect nutrition, imperfect elimination and imperfect health. Verily, "breath is life."
The combustion arising from the change in the waste products generates heat and equalizes the temperature of the body. Good breathers are not apt to "take cold," and they generally have plenty of good warm blood which enables them to resist the changes in the outer temperature.
In addition to the above-mentioned important processes, the act of breathing gives exercise to the internal organs and muscles, which feature is generally overlooked by the Western writers on the subject, but which the Yogis fully appreciate.
In imperfect or shallow breathing, only a portion of the lung cells are brought into play, and a great portion of the lung capacity is lost, the system suffering in proportion to the amount of under-oxygenation. The lower animals, in their native state, breathe naturally, and primitive man undoubtedly did the same. The abnormal manner of living adopted by civilized man—the shadow that follows upon civilization—has robbed us of our natural habit of breathing, and the race has greatly suffered thereby. Man's only physical salvation is to "get back to Nature."