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.