Part 12
The eye-minded person, moreover, has still another string to his bow. Not only can he recall what he has seen; he can also imagine things which he has not seen, and so tell in advance how they are going to look. The engineer about to build a bridge, the architect planning a house, the housekeeper deciding how she shall arrange a room or set a table, the girl considering a new dress, the boy laying out a ball field, all can work to vastly better advantage if they can see exactly how everything is going to look, before they do anything. It is a great deal easier to change things in one’s mind, than after they get into wood and iron and cloth. No one can possibly succeed as engineer, architect, designer, dress-maker, milliner, and the like, unless he can make these pictures in his mind’s eye, and see how things are going to be, before he wastes time and material on the reality, Fortunately, this eye-mindedness is easily cultivated. One has only to attend to his mental pictures, and try to see all there is in them, to have them grow sharper and more complete. In fact, children usually have so much of this faculty that if they only kept what they have, instead of letting it waste away from lack of use, they would be far better off when they grew up than most grown-ups are. As we get older, we get to thinking more in words, and we lose the knack of making pictures. All is, we simply mustn’t.
XXXIV
Ear Minds and Others
Some persons are ear-minded. If you say to them
BREAKFAST TABLE.
they don’t see any breakfast table at all. Instead they hear in their mind’s ear the sound of dishes, the murmur of conversation, and the clatter of knives and forks. When they have learned their lessons, and stand up to recite, they hear an inner voice telling them what to say. They cannot easily remember how places look on the map; but they remember the songs of birds, the different whistles and bells of their neighborhood, they like lectures and readings, and when they have heard a tune once, they know it again. Such people may find it hard to learn to read a foreign language, but they make it up by learning easily to understand it when spoken.
Musicians are apt to be ear-minded. Mozart, for example, could listen to a long piece of music, then go home and hear it over again as many times as he liked in his mind’s ear, and so write it down at his leisure. Beethoven, after he became stone deaf, used still to write his magnificent symphonies, that took hours to perform, making them up in his head and hearing them in his soul’s ear—violins, and trumpets and cymbals and drums, each in its proper place, long after his bodily ears had ceased to hear any noise.
Not many people are ear-minded; not nearly so many are as eye-minded. Those that are, can always hear sweet music and pleasant sounds, whenever they will, and recall the words and voices of their friends. Surely there is much happiness in being ear-minded. Whatever ear-mindedness one has, is well worth hanging on to and improving.
More people are muscle-minded. Think of a
BALL.
Do you see the ball in your mind’s eye? or do you hear the word ball in your mind’s ear? or do you feel the ball in your fingers, and the pull of your muscles as you throw? If the last, you are muscle, or motor-minded, and you probably found yourself saying to yourself the word ball.
Motor-mindedness, too, is a great convenience. It helps to make games come easy, and dancing, and all sorts of gymnastics; it makes it easy to carry oneself properly, to use tools, to be skillful with one’s fingers, to play musical instruments. Motor-minded people are apt to talk easily, and to learn readily to speak foreign languages. Anything, in short, comes easy to them which involves doing something.
Nearly all blind people are motor-minded. If they are also deaf, then of course, they have to be so. I have seen a blind man get off a street car, turn into his street, walk down the street as far as his own gate, and there turn in without the least pause or hesitation, any more than as if he could see. He couldn’t see. He simply felt that he had walked just far enough. And he had.
Do you want to know which of the three possible sorts of minds your mind happens to be? Then think of the street number of your house, or the year in which Columbus discovered America. Did you look for the figures, or listen for them, of try to say them to yourself? Did you see 1492 printed out somewhere, or did you hear something say it; or did you feel yourself saying it in your throat? In the first case you are eye-minded; in the second, ear-minded; in the third, motor-minded.
Most persons are mixed-minded. They have one principal sense, with which they do most of their thinking; but where that is not convenient to use, they employ another. Occasionally even, they use the third. I am myself motor-minded. To learn anything, I say the words over to myself. If anybody tells me anything, I cannot remember it, unless I first say it over; and whenever I think of anything, I say words about it to myself. I can Recognize tunes when I hear them, but I cannot recall a tune, unless I fit it to some words or sounds and think of myself as singing it. But I can think of how things look, or imagine how things will look, much more easily than I can think about how they sound; and I can, with some effort, think how things look without starting to say anything about them to myself in words. So I am also somewhat eye-minded.
Most of you will probably find yourselves, first eye-minded, then motor-minded. That is, on the Whole, the most useful arrangement. But the best sort of mind is one that can handle all three kinds of ideas; and think about seeing, hearing, and doing all about equally well. So you had better notice which you can’t do, and set about learning to do it.
XXXV
Living Automobiles
If you will think back over what you have already learned in this book, you will see that we began by finding out something about how we men, the animals, and the plants come to have any such things as bodies at all. We learned how the little chick forms inside the egg, and the little plant inside the seed. We learned, too, about the wonderful life-jelly or protoplasm of which all living things are made; how it shapes itself into cells; how it builds these cells into our various members, eyes and bones and hair and muscles; and how the body changes, as we grow from youth to maturity, and from maturity to old age.
Then, after we had learned something about this body of ours, we turned to consider how we use it. We found about something of what animals cannot do, and what they can do, and how they do it. We learned how animals of various sorts, and plants as well, see and feel and act; and we learned also something about how we ourselves do our thinking, which is so very different, and so very much better done, than that of any animal or plant.
Now we turn to a different matter. We have taken up being, and doing, and thinking. Now we shall consider living. We shall learn about how the body of the plant or animal feeds itself and keeps alive, and how the different parts of it, the bones and skin and leaves and bark, manage to get on with one another, and work together like a well-made machine.
For, of course, the body is a machine. It is a vastly complex machine, many, many times more complicated than any machine ever made by hands; but still after all a machine. It has been likened to a steam engine. But that was before we knew as much about the way it works as we know now. It really is a gas engine; like the engine of an automobile, a motorboat, or an airplane.
I don’t suppose that any boy, at least, needs to be told the difference between a gas engine and a steam engine. In the one, we build a fire under the boiler, and turn water to steam. Then the steam goes thru a pipe to the cylinder, where it pushes the piston back and forth, first on one side, then on the other, and so turns the wheels.
In the gas engine, on the other hand, there is no boiler, no steam, and no fire. A mixture of air and gasolene vapor flows into the cylinder, cold. There it explodes, set off by an electric spark, and the push of that explosion moves the piston and makes the wheels go round.
We, I say, are not steam engines. We have neither boiler nor steam nor fire. But each little working cell is like a little cylinder, which takes up from the blood air and food, mixes them together inside itself, waits with everything ready to go off, gets the proper signal thru a nerve, then explodes and does something.
That’s the way a muscle does its work. It is a many-thousand-cylindered engine. Each little fiber of the muscle is a cylinder; and each time you lift your hand or move your foot there is a perfect battery of minute explosions. You cannot hear them, for there is no pop—the muffling is vastly better than any engine-builder ever devised. But you do feel the heat; and if you move fast and hard enough, you have to stop to cool off and get a drink.
The plants also are many-cylindered gas engines. They do not do so much work as animals do, not so much running round and moving things. But they do move, and certainly grow and lift themselves high in the air. This much work they do by exploding their cells, just as animals or automobiles do theirs. The growing plants take their food out of the air thru their leaves; and they take also the air itself in the same way. They mix these together inside their cells; and when there is work to be done, growing, moving, or any other sort, they explode a little of the mixture and do it.
Don’t think then that animals and plants and human beings are merely like automobiles. They are automobiles. Their fuel is their food. They mix it with air. They explode the mixture, and move. Anything that does that is an automobile, and runs with a gas engine.
XXXVI
Air and Fuel
We are, then, gas engines. So we have to have air to mix with our gasoline. The simpler water animals, such as sponges, which are mostly holes, and all minute creatures, both animals and plants, simply take it in directly into their cells where they are going to use it. There is plenty of air in water—you can see it fizzle out from the water in a drinking glass when you draw water from a faucet in cold weather. The water creatures breathe this out of the water, and die of suffocation if you put them in boiled water from which the boiling has driven out the air.
Most animals which have blood, use this to carry the air to their cells. For blood, whatever else it is, is nine-tenths water, and will dissolve air like any other water. The insects, however, though they have blood, do not use it to carry air. Instead, they have a system of branching pipes running all over their bodies, and opening at various points on the surface. You can often make these out easily, a pair of openings for each joint, on the sides of caterpillar’s body. These pipes carry the air everywhere over the insect’s body, even to the feet, so that wherever there is a working muscle, there also is the air for it to work with. Thus the insect has no need of lungs, and has none; and therefore, I suppose never gets out of breath, no matter how hard it works.
We human beings, and our four-footed cousins, all backboned animals in fact, do not manage in any of these ways. We breathe the air into our lungs. There, instead of dissolving it in the watery part of the blood, we turn it over to the red corpuscles, which are especially made to do this very thing and do it particularly well. These minute, coin-like corpuscles carry the air all over the body, and deliver it over to the cells as they need it. But of course, as you must have already learned in school, the body handles only the part of the air that it can use, the oxygen. The rest it lets go and doesn’t bother with. That is where we have the advantage over other automobiles, which can’t pick out the part they want but have to take the air as it comes. Still it all comes to the same thing in the end. With all animals the oxygen gets mixed with the fuel and explodes.
Our fuel, moreover, is a good deal like gasoline. Gasoline, as you know, is related to kerosene, benzine, paraffine, and the rest, which are all products of rock oil. They are, then, themselves oils; and gasoline is an oil.
We, too, eat oils; not, to be sure, mineral oils, but animal and vegetable oils, olive oil and butter and cream and all sorts of fats; for fats are merely oils that freeze at common living temperatures and melt only after we get them stowed away.
We, then, burn many sorts of oil. We also burn bread and potatoes and the like, starch and sugar and gums, which though not oils, are much like them; really in a way, oils that are already about half burned. These we finish up in our engines. On the whole, it’s much more convenient than depending on one sort of fuel, and exploding only gasoline.
I am not going to stop now to tell you the long story of how the bread and potatoes and the rest of our food finally gets changed over into a sort of sugar; and is as sugar, packed away in the cells of our muscles and other tissues, mixed with the oxygen of the air, and made ready to explode when the signal through the nerve touches it off. The food is taken apart and put together again, combined and separated, stored up when it isn’t needed, and used sometimes in one way and sometimes in another. Different animals treat their food differently after they get it swallowed; even different human beings, eating the same food, do not always handle it quite the same way.
Most of us take our food into our stomachs, but the earthworm crawls through the earth, and at the same time lets a stream of earth crawl through him, digesting what is food and leaving the rest behind as he moves along. Amoebas sometimes flow round little water plants many times longer than themselves, crawl along the stem, with the stem sticking out front and back, and digest the juices as they go along. The star-fish, which lives on oysters larger than himself, turns his stomach inside out, sticks it into the oyster’s shell; and after he has digested the oyster, pulls his stomach back again. A dog will digest bones; and a cow will digest wood; while a fish will swallow another fish nearly as long as himself, keep the tail, still unswallowed, in his mouth while he digests off the head, and than moves his meal up another notch.
There are all sorts of queer freaks, but the main point is that, in the end, all our food gets built into the cells of our bodies; much of it in the form of sugar, and that this sugar explodes as if it were the gasoline vapor in a gas engine that some man has made. With the force of these explosions, the body does its work; it keeps itself warm with the waste heat.
XXXVII
Men In Glass Boxes
One curious thing about these explosion engines of ours is that, when all goes well with our little insides, we get just exactly the same amount of work out of each mouthful of our food, that we should get, if we should dry the food, grind it to fine dust, and explode the dust mixed with air in the cylinder of an automobile—as it would be quite possible to do, if one wanted to take the trouble.
In fact, the United States Government, for several years, set people to trying just this very thing, by way of finding out how much work can be got out of various sorts of food, and out of which sorts a man can get most for his money. They have a big glass box, as large as a state-room on a steamer, with a bed in it and a table and chairs, and also a stationary bicycle, on which one can ride without moving, and so get his exercise. They put a man in this box, and keep him there for a week. They weight carefully everything that he eats and drinks; and each time he takes a meal they find out, by drying some of the food and burning it and measuring the heat they get from the burning, just how much that food is worth as fuel. Thus they know how much exploding he ought to be able to do in his tiny cylinders.
Then in addition, they keep track of all the air that goes into the glass box, and find out just how much oxygen he uses up to explode the food. They see also how much he heats up the air which comes out of the box by the warmth of his breath, the heat of his body, and the friction of the stationary bicycle when he exercises.
It always turns out that the man makes just as much heat out of the food he eats as the same food would yield if dried and burned; and that it takes just as much air to explode it in his body as it would take to burn it in a stove. So the body is really an engine. It uses up fuel like any engine; and gets the same amount of heat or work out of its fuel as any other well-made engine would.
As a result of these experiments, and others like them, the United States Department of Agriculture has issued a pamphlet, called Bulletin Number 28, which tells, among other things, how much work one ought to be able to do on one pound of almost any sort of food that any civilized human being would ever think of eating. I trust that every girl who reads this book, before she grows up, and goes to keeping house, and has to feed a family, will get this little pamphlet, or something else like it, and study carefully what different foods are really good for. According to the United States Government, a child can do more hard playing, and a man more hard work, on one pound of bread, spread with four ounces of butter, than eight pounds of broiled spring chicken; while ordinary dry crackers and cookies are twice as nutritious as lean meat, and six times more nutritious than oysters, lobster, and most sorts of fish.
Still, there is this most important difference between our living engines and the engines which we build of brass and steel. When a part wears out or breaks in an automobile, if it cannot be mended, it has to be thrown away. But in the body, when a part of the life-jelly wears out, as it is continually doing, we not only make some new to take its place, but we use up the old stuff as fuel to drive the engine.
In short then, some automobiles are built of steel and leather and brass and rubber, and burn gasoline. And some are built of life-jelly and burn sugar. The first sort, when it wears out, we mend with more steel and leather and brass and rubber. The second sort, when it wears out, we mend with more life-jelly, which we get from the portion of our food that is neither sugar nor starch nor oil, but the once living jelly of other plants and animals, which I am sorry to say, we have to kill to get stuff for our own repairs. The plants can make their life-jelly out of the air that they take in thru their leaves and the water that comes in through their roots. But we animals, from the least to the greatest, can get it only by taking it away from something else. For my part, I feel easier in my mind when I take away this life-stuff from some plant like wheat or corn, than when I rob some breathing animal like myself.
XXXVIII
Of Sugar and Other Poisons
Our bodies, therefore, and the bodies of all other animals, are gas engines, which burn sugar by exploding it mixed with air. Most of our food, to be sure, isn’t sugar, but bread and potatoes and cookies and all sorts of nice things made of butter and flour, milk and the like. But as I have already pointed out, the most important portion of this food is either made over into our own life-jelly, or else it is changed into sugar and exploded in our muscles.
Sometimes when the automobile goes by, one of the things you notice is a very bad smell. This is largely the unburned and half burned gasoline. Gasoline, when it burns clean, changes to water and to the odorless and slightly tangy gas which we get in soda water, carbon dioxid as it is called. When you burn gasoline, then, you get the same products as if you boiled plain soda water.
Most things that burn, likewise, burn to carbon dioxid and water. Wood does it, and coal, all kinds of oil that we burn in lamps, and the gas that we burn for light and heat. So, too, do all sorts of candles—paraffin, for example, or wax; and so, too, do the old fashioned tallow candles which our great-grandmothers used to make. Tallow, however, is a fat, except for its taste, like the fat we eat. Practically, we eat nothing that we cannot also burn, when dry—tho we do burn a good deal that we cannot eat.
Most of these burnable foods explode in the body, a good deal as they burn outside. They form carbon dioxid and water—when you “see your breath” on a cold day, you merely see the water in it that came from your exploding muscles. If you eat largely only plain wholesome foods, bread and butter, fresh vegetables, fruit, candy and cookies and crackers, and all the various other foods that burn clean, they will burn clear in your bodies, and you will yourselves be clean and sweet as children ought to be. But if you have a taste for things you ought not to have, and get them, then instead of good clean water and carbon dioxid, you will explode to a lot of unwholesome, poisonous, and smelly things, that are not at all nice outside the body, and are still worse inside.
Unfortunately, we cannot live altogether on these clean-burning fats and starches and sugars, which explode to carbon dioxid and water, and leave nothing more behind than a wax candle when it burns. We can’t make our life-jelly out of these foods. So we have to eat also, eggs and milk and cheese and beans and peas and meat and fish, some parts of which we can build to our life-jelly. But only about a tenth part of our food needs to be of any of these life-jelly-making sorts. The other nine-tenths should be the clean-burning things with which we do most of our work and play.
But whatever the fuel with which we run our bodily engines, sooner or later it gets used up and the waste products have to be blown off into the air. Insects and automobiles, which take the air pretty directly into their cells, blow off their waste gases directly into the air again. The lowly creatures which breath the air in the water, send their carbon dioxid back into the water again. But we who have blood, use that to carry off our exploded sugar and other things.
The water of the burned up food is simply added to the watery part of the blood. The carbon dioxid becomes in the blood ordinary cooking soda; the blood carries the soda to the lungs, and there it changes to carbon dioxid again, exactly as it does when, as cooking soda, or baking powder, you add it to flour and use it to raise cake. Finally it comes out of the lungs with the breath, and that is the end of it so far as we are concerned.
Still, we are not through with it yet; because the plants take in thru their leaves the carbon dioxid that we animals breath out thru our lungs, take it apart again, mix it up with water and other things which they get thru their roots, and finally make it over into wood, and into starch and sugar and the like which we animals eat up once more. So if we eat the plants, the plants also eat us; and the same stuff keeps getting used over and over again. And a mighty convenient arrangement it is, too, since there is precious little stuff to make living things out of in the world at best. Most of the earth is just rocks.
However, I started to tell you something about the burnt up food and exploded muscle-sugar, While it is still in the body, before blood and lungs and skin and kidneys have combined to carry it away.