How and Why We Breathe : Part 2

A Handbook of Health
by Woods Hutchinson

(Page 15 of 29)

The lungs sprout out from the front of the gullet, just below the root of the tongue, in the days when we are getting ready to be born. The sprout divides into two, forming the beginning of the pair of lungs. Each lung sprout again divides into two, and each of the two smaller buds again into two, until finally we have the whole chest filled up with a "lung-tree" whose trunk stems and leaves are hollow. The stem of the tree or bush becomes the windpipe (trachea). The first two branches into which it divides form the right and left lung tubes, known as bronchi. The third, fourth, fifth, sixth, etc., divisions, and so on, form what are known as the bronchial tubes. These keep on splitting into tinier and tinier twigs, until they end, like the bush, in little leaves, which in the lung, of course, are hollow and are called the air cells (alveoli). This budding off of the lungs from the gullet is the reason why the air we breathe and the food we swallow go down the same passage. Every mouthful of our food slides right across the opening of the windpipe, which has to be protected by a special flap, or trap-door of gristle, called the epiglottis. If you try to eat and talk at the same time, the epiglottis doesn't get warning of the coming of a swallow of food in time to cover the opening of the windpipe, and the food goes down the wrong way and you cough and choke.

Now, if you will just place your fingers upon the front of your neck and slide them up and down, you will, at once, feel your windpipe - a hard, rounded tube with ridges running across it, - while, no matter how carefully you feel, or how deeply you press, you cannot feel your gullet or esophagus at all. Just take a mouthful of water, however, put your fingers deeply on each side of the windpipe, and swallow, and you will feel something shoot down the esophagus, between your fingers, toward the stomach.

Both of these tubes were made of exactly the same materials to begin with. Why have they become so different? A moment's thought will tell you. One, the gullet, has only to swallow solid food or drink, so that its walls can remain soft, and indeed fall together, except when it is actually swallowing. The other tube, the air-pipe or windpipe, has to carry air, which neither will fall of its own weight, nor can readily be gulped down or belched up. It is absolutely necessary that its walls should become stiff enough to keep it open constantly and let the air flow backward and forward. So we find growing up in the walls of this air pipe, cells which turn themselves into rings of gristle, or cartilage.

What the Breath Is. As you know, your "breath," as you call it, - that is to say, the used-up air which you blow out of your lungs, - is different in several ways from pure, or unused air. In the first place, it is likely to have a slight musky or mousy odor about it. You never like to breathe any one else's breath, or have any one breathe in your face. This dislike is due to certain gases, consisting of impurities from the blood, the cells of the lungs, the throat, the nose, and, if the mouth is open, the teeth. These are not only offensive and disagreeable to smell, but poisonous to breathe.

Then your breath is much warmer than the rest of the air. In fact, on a very cold morning you may have tried to warm up your fingers by breathing on them; and you have also noticed that if a number of people are shut up in a room with doors and windows closed, it soon begins to feel hot as well as stuffy. This heat, of course, is given off from the blood in the lungs and in the walls of the throat and nose, as the air passes in and out again.

When you stand at the window on a cold day, the glass just in front of your mouth clouds over, so that you can no longer see through it; and if you rub your finger across this cloud, it comes away wet. Evidently, the air is moister than it was when you breathed it in; this moisture also has been given off from the blood in the lungs.

But what of the principal waste gas that the blood gives off in the lungs - the carbon "smoke," or carbon dioxid? Can you see any trace of this in the breath? No, you cannot, for the reason that this gas is like air, perfectly clear and transparent, and never turns to moisture at any ordinary temperature. But it has a power of combining with certain other things and forming substances which, because they are combinations of carbon, are called carbonates. The commonest substance with which it will do this is lime. If you take a glass or a bottle two-thirds full of lime water, and breathe into it through a glass tube or straw, you will see in a very few minutes that it is becoming milky or cloudy from the formation of visible carbonate of lime, which, when you get enough of it, makes ordinary limestone. So, although you cannot see, or smell, this carbon "smoke" in your breath, you can readily prove that it is present.

How and Why our Breathing Varies. When you run or wrestle, you breathe faster in order to draw more air into the lungs. At the same time, your heart beats faster in order to drive a larger amount of blood through the lungs. If you run too far, or wrestle too hard, your heart and your lungs both go faster and faster, until finally they reach a point when they cannot go any quicker, and the poisonous waste substances are formed in your muscles faster than they can possibly be burned up, even by the quickest breathing and the hardest pumping of your heart. Then you begin to get "out of breath"; and if you were compelled - in order to save your life, for instance - to keep on running, or fighting, you would at last be suffocated by your own waste and dirt, and fall exhausted, or unconscious.

On the other hand, by carefully training your muscles and your heart and your lungs by exercises of various sorts in the open air, beginning with easy ones and going on to harder and longer ones, you can "improve your wind," so that your heart will be able to pump more blood through the lungs per minute, and your lungs will be able to expand themselves more fully and more rapidly without fatigue.

If you can recall having had a fever of any sort, even a slight one, such as comes with a sore throat or a bad cold, you may remember that you breathed faster and that your heart beat faster, and yet you were not doing any work with your muscles. The cause, however, is the same; namely, the amount of waste that is being produced in the body - in this case, by the poisons (toxins) of the germs that cause the fever. The more waste that is formed in the body, the more effort the heart and lungs will make to try to get rid of it.

The Ribs. How does the air get in and out of the lung tubes? Evidently you do not and cannot swallow it as you would food or drink; and as it will not run down of its own accord when you simply open your mouth, nature has had to devise a special bit of machinery for the purpose of sucking it in and pressing it out again. This she has done in a rather ingenious manner by causing certain of the muscle-rings in the wall of the chest to turn first into gristle, or cartilage, and then later into bone, making what are known as the ribs; these run round the chest much as hoops do round a barrel, or as the whalebone rings did in the old-fashioned hoop skirt. When the muscles of the chest pull these ribs up, the chest is made larger, - like a bellows when you lift the handle, - air is sucked in, and we "breathe in" as we say; when the muscles let go, the ribs sink, the chest flattens and becomes smaller, the air is driven out, and we "breathe out."

Houghton Mifflin Company
Copyright, 1911, By Woods Hutchinson
All Rights Reserved
Tenth Impression

About the Author

Woods Hutchinson (1862-1930) was an American physician, born at Selby, Yorkshire, England. He graduated from Penn College, Oskaloosa, Iowa, in 1880 and received his medical degree from the University of Michigan four years later. He worked as a professor of anatomy at the State University of Iowa and then became a professor of comparative pathology at the University of Buffalo.