( Originally Published 1920 )
The Importance of Breathing. When someone has asked you what you were doing, you have probably often answered, "Nothing." That was not quite accurate, however, was it? There are some things, you are doing all the time, and one of the most important of these is breathing.
In and out, in and out, the air goes every minute of the day and night, whether you are working or playing or sitting still or asleep in bed. Put a watch on the table before you, and count the number of breaths you take in one minute. Then multiply the number by 6o to see how many times you breathe in an hour, and multiply that product by 24 to see how many times you breathe in a day. All through your life this must go on. If breathing stopped for a very few minutes, the whole machinery of the body would stop too.
The Organs of Breathing.—Where does the air go that you breathe in so many times a minute? If you will look at Fig. 46, you will see.
The air, drawn in through the nose, passes first. into the upper part of the throat, for the nose opens into the throat, as you can see by the picture. From the lower part of the throat there are two openings. Through the opening at the front, the air is drawn into the windpipe; and at the back there is an opening into the esophagus, by which food passes to the alimentary canal. The wind-pipe (see Fig. 47) runs your down a little way and then divides into two branches, called bronchi which lead to the lungs. The two lungs are the principal organs of breathing, or respiration. It is through the nose, throat, and windpipe that the air we breathe passes down into the lungs.
The lung is made up, for the most part, of a great number of small air chambers. All of these chambers are connected with the windpipe. You have just seen that the windpipe is divided into two bronchi; these two bronchi subdivide again into many fine branches that go to all parts of the lungs.
In the walls of the branches and of the. tiny air chambers is a network of fine blood vessels. The blood flowing through these blood vessels is separated from the air in the lung by a very thin layer of living matter. Through this thin layer, substances in the air may pass into the blood, and substances in the blood may pass out to the air.
The Air We Breathe.—What is there in the air that the body needs?
The air seems like nothing at all. We cannot see it, and can feel it only when there is a wind or some other force to set it in active motion. Yet the air is a very real substance, or mixture of substances.
We live in an ocean of air and depend upon it for our life, just as fish live in the water and die when taken out of it. Some things, like salt and stones, are solid; some, like water and syrup, are liquid; and some that move about freely, mixing with the air and often, like it, invisible, are gases. You know about the gas that comes into our houses in pipes and is burned for heat and light. This is only one kind of gas. The substances in the air are gases, too.
The Good Fairy Oxygen. When illuminating gas burns, there is a chemical action going on between two gases; the illuminating gas that came in through the pipe combines with a gas, called oxygen, in the air of the room. Wherever anything burns, it is this gas, oxygen, which is at work. If a candle flame were covered over with a tight glass jar, the candle would go out as soon as it had used up all the oxygen of the air inside the jar. For the activities of the living matter in our bodies, we need oxygen, just as the candle flame does. The first object of respiration is to supply oxygen.
It is this gas which passes from the air chambers of the lungs into the blood, as we breathe. The more you learn about oxygen, the more you will feel that it is almost like one of the good fairies in the story books. You cannot see it, but it is every-where about us. Whenever any one strikes a match or lights a fire, Oxygen is at work making the flame burn. The fire of logs around which some band of travelers gathers for warmth in the frozen north, and the great blast furnaces of Pittsburgh where steel is made for mighty ships and for guns, owe their heat and their power to Oxygen. It is Oxygen which makes possible the life of every living thing, from the green slime on the bark of a tree to the tree itself, and from the tiniest insect up to the elephant or man.
Objects of Respiration.—Getting oxygen into the body is only one of the objects of breathing. It is almost equally essential to get rid of certain wastes formed in the body itself. Chemical changes are going on all the time in living matter, and waste substances are being formed, which would injure the body if they were not carried away. One of the most important of these wastes is a gas called carbon dioxide, which is carried away from the different organs by the blood and finally gotten rid of through the lungs.
In the walls of the tiny air spaces of the lungs, there is a thin layer of living matter with blood on one side and air on the other. Oxygen passes in from the air to the blood, and carbon dioxide passes out from the blood to the air.
In this way the air in the air chambers of the lungs would, of course, become all the time poorer in oxygen and richer in carbon dioxide, if it were not changed.
Our constant breathing in and out is necessary in order to change the air in the lungs, to bring in fresh oxygen, and carry off carbon dioxide.
Besides carbon dioxide, a good deal of water is given off to the air in the lungs. On a cold day we can see this water condensed as moisture from the breath.
The Old Well.—Two boys were once playing ball on a farm in eastern Connecticut when the ball, which had been thrown a little wild, bounded into an old, unused well and disappeared. The boys peered over the edge and threw a stone in. They could tell by the noise as it struck that there was earth and not water at the bottom.
The walls of the well were made of rough stone; and although it was quite deep, Edward, the elder boy, who was strong and active, thought he could climb down by getting his toes in between the stones and holding on to the old well rope, which was. made fast at the top. He had kicked off his shoes when the younger brother, Robert, had a sudden thought. "Wait a minute, Ed," he said, "let us be sure first that the air is all right."
He ran to the house and brought back a candle and some matches and a long piece of string. The boys' father, who was passing, joined them to see what was going on. He helped them cut a groove around the candle, tie a string in the groove, light the candle, and let it slowly down into the well. When it was nearly at the bottom,—all at once the candle went out
"Well, boys, what does that mean?" asked their father.
"Why, it means that there was not enough oxygen down at the bottom of the well to keep the flame burning," cried Robert in excitement, "and if Ed had gone down, there would not have been enough for him to breathe and he might have died."
"Right you are," said his father. "There is plenty of oxygen in all ordinary air, even in crowded rooms; but in old wells and cesspools and the lower parts of mines, where decay is going on, the air sometimes contains a great deal of carbon dioxide and not enough oxygen to support life. You have studied physiology to good purpose, Bob, I see, and I will give you a new League ball for your good sense and judgment."
How the Breathing Movements are Made: The machinery by which the breathing movements are made and the air is drawn into the lungs is one of the most interesting things about the human body.
The lungs lie in the chest, in a space bounded on the sides by the ribs and below by a very large muscle called the diaphragm (see Fig. 9). The diaphragm is shaped like a big saucer upside down.
Each time we take a breath, two things happen_ In the first place, the muscles of the ribs contract so as to pull the ribs upward and outward, which makes the chest space larger from front to back and from side to side. This is the movement we see as we watch the chest rise when a person breathes deeply. At the same time, the diaphragm contracts so as to pull its center downward (flattening out the inverted saucer) ; this makes the chest space larger from top to bottom. The walls of the lungs are elastic, and anything that makes the chest space larger will make the lungs grow larger, too. As they grow larger, they draw air in through the windpipe from the throat.
These two sets of muscles contract and relax each time we breathe. What is more wonderful still, they change so as to regulate rate and depth of breathing to meet all the changing conditions of our life. When you run, for instance, the muscles that are working hard need more oxygen and make more carbon dioxide that must be got rid of. So without any planning on your part, the muscles of breathing do more work, and the breaths come more quickly, and the lungs are filled more completely.
The Hygiene of the Breathing Organs.—A full use of the organs of respiration is essential for the health of the body. Anything which hinders the chest movements or cramps the lungs is likely to prevent the full, deep breathing which we need in order to keep well. Wearing tight clothes and sitting or standing in a slouching position have, therefore, a bad effect on the breathing organs.
It is an excellent plan to take a few exercises in deep breathing every morning. Hold your head up and your body straight. Then raise your arms slowly at your sides as you breathe in, and let them slowly fall as you breathe out.
You should always breathe through the nose and not through the mouth. In passing through the nose, the air becomes warmed, and dirt particles in it are taken out, because they stick to the moist surfaces of the nose. Breathing cold air and dust-laden air directly into the throat through the mouth is a dangerous habit. If you cannot breathe comfortably through your nose, there is something wrong, and you should go to a doctor for examination. The doctor will know how to remedy the difficulty, and you will be able to work and play and study better when you breathe properly through the nose.
The walls of the breathing organs are very soft and delicate, and microbes often grow upon them, as they do in cavities of the teeth, and cause disease. When this happens in the nose or the upper part of the throat, we may call it a cold in the head or a sore throat. If it occurs in the branches of the windpipe (the bronchi), it is bronchitis; if in the lungs themselves, pneumonia.
In the back of the throat are two roundish organs called the tonsils, which you can see on each side as you look into the mouth. These organs are particularly liable to be diseased, the trouble which results being called tonsilitis.
We can avoid these diseases by keeping the microbes that cause them out of the mouth and nose, as far as possible, and by keeping the nose and throat and other organs of respiration so healthy that they can resist any germs which do come along. Both these subjects will be discussed in detail in a later chapter.
The Organs of Speech: At the top of the windpipe, just below the point where it connects with the throat, is a small but very important organ, called the larynx (see Fig. 47). The larynx has in it two bands called the vocal cords, which make many of the sounds of speech. The cords vibrate in certain ways, like the strings of a violin or a piano. If you place your fingers on your throat under the chin when speaking, you can feel the larynx moving. The larynx does not do all of this work, however, for many of the sounds of speech are made with the lips, teeth, and tongue. Say over the letters of the alphabet and see which ones require the use of these various organs.