A Handbook of Health. Woods Hutchinson
PLATES IN COLOR
facing 110 Diagram of the Circulatory System
facing 198 Diagram showing General Plan and Position of Body-Machinery
A HANDBOOK OF HEALTH
CHAPTER I
RUNNING THE HUMAN AUTOMOBILE
The Body-Automobile. If you were to start to-morrow morning on a long-distance ride in an automobile, the first thing that you would do would be to find out just how that automobile was built; how often it must have fresh gasoline; how its different speed gears were worked; what its tires were made of; how to mend them; and how to cure engine troubles. To attempt to run an automobile, for even a ten-mile ride, with less information than this, would be regarded as foolhardy.
Yet most of us are willing to set out upon the journey of life in the most complicated, most ingenious, and most delicate machine ever made—our body—with no more knowledge of its structure than can be gained from gazing in the looking-glass; or of its needs, than a preference for filling up its fuel tank three times a day. More knowledge than this is often regarded as both unnecessary and unpleasant. Yet there are few things more important, more vital to our health, our happiness, and our success in life, than to know how to steer and how to road-repair our body-automobile. This we can learn only from physiology and hygiene.
The General Plan of the Human Automobile is Simple. Complicated as our body-automobile looks to be, there are certain things about the plan and general build of it which are plain enough. It has a head end, where fuel supplies are taken in and where its lamps and other look-out apparatus are carried; a body in which the fuel is stored and turned into work or speed, and into which air is drawn to help combustion and to cool the engine pipes. It has a pair of fore-wheels (the arms) and a pair of hind-wheels (the legs), though these have been reduced to only one spoke each, and swing only about a quarter of the way around and back again when running, instead of round and round. It has a steering gear (the brain), just back of the headlights, and a system of nerve electric wires connecting all parts of it. It gets warm when it runs, and stops if it is not fed.
There is not an unnecessary part, or unreasonable "cog," anywhere in the whole of our bodies. It is true that there are a few little remnants which are not quite so useful as they once were, and which sometimes cause trouble. But for the most part, all we have to do is to look long and carefully enough at any organ or part of our bodies, to be able to puzzle out just what it is or was intended to do, and why it has the shape and size it has.
Why the Study of Physiology is Easy. There is one thing that helps to make the study of physiology quite easy. It is that you already know a good deal about your body, because you have had to live with it for a number of years past, and you can hardly have helped becoming somewhat acquainted with it during this time.
You have, also, another advantage, which will help you in this study. While your ideas of how to take care of your body are rather vague, and some of them wrong, most of them are in the main right, or at least lead you in the right direction. You all know enough to eat when you are hungry and to drink when you are thirsty, even though you don't always know when to stop, or just what to eat. You like sunny days better than cloudy ones, and would much rather breathe fresh air than foul. You like to go wading and swimming when you are hot and dusty, and you don't need to be told to go to sleep when you are tired. You would much rather have sugar than vinegar, sweet milk than sour milk; and you dislike to eat or drink anything that looks dirty or foul, or smells bad.
These inborn likes and dislikes—which we call instincts—are the forces which have built up this wonderful body-machine of ours in the past and, if properly understood and trained, can be largely trusted to run it in the future. How to follow these instincts intelligently, where to check them, where to encourage them, how to keep the proper balance between them, how to live long and be useful and happy—this is what the interesting study of physiology and hygiene will teach you.
CHAPTER II
WHY WE HAVE A STOMACH
WHAT KEEPS US ALIVE
The Energy in Food and Fuel. The first question that arises in our mind on looking at an engine or machine of any sort is, What makes it go? If we can succeed in getting an answer to the question, What makes the human automobile go? we shall have the key to half its secrets at once. It is fuel, of course; but what kind of fuel? How does the body take it in, how does it burn it, and how does it use the energy or power stored up in it to run the body-engine?
Man is a bread-and-butter-motor. The fuel of the automobile is gasoline, and the fuel of the man-motor we call food. The two kinds of fuel do not taste or smell much alike; but they are alike in that they both have what we call energy, or power, stored up in them, and will, when set fire to, burn, or explode, and give off this power in the shape of heat, or explosions, which will do work.
Food and Fuel are the Result of Life. Fuels and foods are also alike in another respect; and that is, that, no matter how much they may differ in appearance and form, they are practically all the result of life. This is clear enough as regards our foods, which are usually the seeds, fruits, and leaves of plants, and the flesh of animals. It is also true of the cord-wood and logs that we burn in our stoves and fireplaces. But what of coal and gasoline? They are minerals, and they come, as we know, out of the depths of the earth. Yet they too are the product of life; for the layers of coal, which lie sixty, eighty, one hundred and fifty feet below the surface of the earth, are the fossilized remains of great forests and jungles, which were buried millions of years ago, and whose leaves and branches and trunks have been pressed and baked into coal. Gasoline comes from coal oil, or petroleum, and is simply the "juice" which was squeezed out of these layers of trees and ferns while they were being crushed and pressed into coal.
How the Sun is Turned into Energy by Plants and Animals. Where did the flowers and fruits and leaves that we now see, and the trees and ferns that grew millions of years ago, get this power, part of which made them grow and part of which was stored away in their leaves and branches and seeds? From the one place that is the source of all the force and energy and power in this world, the sun.
That is why plants will, as you know, flourish and grow strong and green only in the sunlight, and why they wilt and turn pale in the dark. When the plant grows, it is simply sucking up through the green stuff (chlorophyll) in its leaves the heat and light of the sun and turning it to its own uses. Then this sunlight, which has been absorbed by plants and built up into their leaves, branches, and fruits, and stored away in them as energy or power, is