Ernest G. Martin

“ When the development of the child has gone far enough so that it can do its own breathing, feeding, and discharging of waste materials, it is expelled from the body of the mother in the process that we know as birth. This does not imply by any means that parental care and responsibility are at an end. Food, protection, and warmth must be provided. Education must be attended to, for the nervous system of the new-born infant is absolutely undeveloped. It has, through heredity, certain possibilities of achievement; their realization hinges upon the bringing to bear of worth-while influences. ”

“ But while motion is the thing we look for in living animals we know perfectly well that it would be foolish to assert that anything that moves is alive. When the wind is blowing the air may be full of dead leaves and butterflies, all moving, but only part, the butterflies, alive. ”

“ We have always known that the locomotive operates by the burning of coal or oil in the fire box. A moment’s thought will show us, if we have not realized it before, that the explosion of the air-gas mixture in the automobile cylinders is also a burning. Every steam-driven power plant depends on burning fuel for its power. Evidently fuel materials contain abundant power, if it can be extracted, and burning is a good method for doing the extracting. The word “burning” is the common name for a chemical process known technically as “oxidation,” meaning the union of oxygen with the fuel. ”

“ Since from time immemorial human beings have habitually eaten every day this large surplus, it is evident that they have been wasting enormous amounts of good food or else that some use is made of it even though it does not serve its purpose of repairing the body waste. The surplus materials are present in the body in the form of amino acids, since what the cells do in repairing their wastage is to take up from the whole quantity of amino acids in the tissue fluids as much as they require for making good their loss. ”

“ What we call an infection is the invasion of the body from the outside by minute living organisms, either plant or animal, and the establishing of them within the body, so that they grow and multiply. They carry on their metabolism just as do all other living cells and produce various chemical products as a result. There are many organisms living within our bodies whose metabolic products apparently do us no harm, and so we serve as hosts for these unbidden guests year in and year out without even knowing of their existence. ”

“ The sight of an automobile which is not alive behaving as though it were because it is under control of a driver who is alive may lead us to ask whether the animal that we know to be living is actually alive in all its parts, or is a dead mechanism of some sort which has somewhere within it a living controller, corresponding to the living driver of the car. The animals with which we are most familiar are ourselves; how is it with our own bodies? Are they alive in all their parts, or is the brain the only part of us which is living? ”

“ Evidently what the Martian explorers missed was the fact that the automobile does not really start or stop itself, or guide itself past obstructions. If it had been alive, it would have done these things of itself. It is not so much the power of motion, then, that proves that the thing is alive as the power of making motions that are under the control of the animal itself. ”

“ We know that a well-constructed machine can operate day in and day out without having to stop to rest; why cannot our muscles do the same? Evidently the necessity of resting cuts down the possibilities of life more than any other one thing; our real life is only two-thirds as long as it counts up in years because we have to spend one-third of the time in sleep. Of course muscular fatigue is not the only kind; there is nervous fatigue, as well, about which something will be said later. The activity of our muscles is based on functional metabolism ”

“ Loud noises or penetrating smells must be endured, but by shutting our eyes tightly we can escape sight whenever we want to. Altogether there are three kinds of information which the sense of sight brings to us; the first is the knowledge simply of light and darkness; the second is the knowledge of the shape and size of objects; the third is the knowledge of color. Nearly all animals seem to have some power of distinguishing between light and shade. Even the one-celled kinds, that have no eyes or anything corresponding to eyes, behave in a way that proves them to have this power. ”

“ Hunger is usually felt just as mealtime draws near, and it is often much keener at noon or night than before breakfast, although the stomach has been longer empty at breakfast than at any other meal. A curious fact about hunger is that it may disappear completely after a few days of complete starvation. Contrary to the popular idea that hunger becomes more and more acute as starvation continues, the testimony of practically all persons who have starved for more than a few days is that all sensations of hunger, as well as all strong longings for food, subside and do not return. ”

“ Nearly everyone learns in school the main facts about the construction of the body; that there is a bony skeleton which supports the softer parts; that motions are made by muscles; that sense organs inform us as to what is going on in the world around; that the brain is the seat of the mind; that heart, lungs, stomach, kidneys, and other organs contribute in various ways to our well-being. ”

“ As labor-saving machines tend more and more to diminish the amount of muscular labor that most of us do, we find it harder and harder to maintain good digestion on fried foods. The objection to frying is simple; fats are the hardest of all foods to digest and fried foods are smeared all over with fat. It is only logical to expect fried foods to be harder to digest than other kinds; it is undeniable that the flavor of many fried foods is so agreeable that we would be unwilling to omit them from the diet altogether. ”

“ On the other hand, the common mixed diet which all of us eat in accordance with custom and the dictates of our appetites has the sanction of thousands of years of successful maintenance of the human race. It is quite true that one can get along on almost any kind of a diet provided it contains enough protein to make good the daily body wastage and enough fuel material to provide for the demands of metabolism. Anyone who is disposed to adopt for himself a dietary fad will rarely suffer seriously from it ”

“ Ordinarily in the body sugar is always present, but in a certain disease, diabetes, about which more will be said later, the body is not able to burn sugar as well as it ordinarily does, and under these circumstances poisoning from the products of the fat burning is apt to happen. This makes up, in fact, the serious danger in diabetes. As we all know, fat is chiefly important as the form in which food is stored in the body against a time of future need. We shall return to the way in which the body does this after we have spoken of the use of sugar as fuel. ”

“ From what we have just said it is evident that the proper emptying of the stomach and, therefore, the proper carrying on of the whole process of digestion, depends upon the formation and outpouring of ample supplies of acid-containing gastric juice. A failure of gastric secretion is bound to be followed by a failure of the stomach to empty itself. Instead of going on to the small intestine where digestion is completed and the digestion products passed on to the blood stream to be used by the body, the food mass lies inert in the stomach. ”

“ What we want to do first is to point out how this notion must affect our views of heredity. If the germinal tissue is simply harbored and nourished by the body, but otherwise quite independent of it, it follows as a matter of course that things the parent does, provided that they do not disturb the nourishment of the germinal tissue, can have very little effect upon it. For example, anything that the parent may achieve during his lifetime cannot be passed on by heredity to his offspring. This is entirely contrary to the idea of heredity which is held by nearly everybody. ”

“ The energy that comes to us from the sun is chiefly in the two forms of heat and light. In actual horsepower the heat far outweighs the light, but in importance to mankind one stands about on a par with the other, for while without the sun’s heat the earth would become so cold that we would all die, without its light there would be no food and we would all starve. This is another way of saying that the energy that plants store up, and that we get when we eat them, comes originally from the light of the sun. Plants, like animals, are made up of cells. ”

“ First of all, in describing the various kinds of metabolism that cells may show, we have the metabolism of rest. By this we mean the power development that is going on when the cell is doing nothing more than keeping alive; neither growing nor showing any special activity. This is evidently the minimum amount that any cell can show, so it is often referred to as the basic metabolism. We know of at least two things that may change the amount of basic metabolism; the first of these is a change in temperature; when a cell is cold, its basic metabolism is less than when it is warm. ”

“ Of course in ourselves, after we have reached full size, there is little or no increase in permanent bulk even though we do keep right on eating. Evidently in the tiny one-celled animal, and in us as well, food is constantly being used for something besides growth. It can be proved that this food is used for precisely the same purpose that gasoline is used in the automobile, namely to run the machine. In a very real sense every living thing is a machine, and will no more run without a supply of power than will any other machine. ”

“ It is much harder to make out the manner of the working of tiny pieces of machinery than of those that are of convenient size. When the parts are as small as those that make up our bodies, the task of finding out how they operate is so difficult that even now, after years of study, there are many details about which we know very little.
The construction units have been named cells. In some tiny animals the whole body consists of but one cell; all higher animals, including ourselves, have millions of cells making up the body. Undoubtedly some cells are alive ”

“ When we come right down to it we could spare our other organs—heart, lungs, stomach, and the rest—and never miss them so far as adding anything to our happiness is concerned. In fact, the less these organs intrude themselves into our attention the better off we are; only when we are ailing do we begin to think about them. Of course, they are absolutely necessary to us, and we should die instantly if one of the more important of them were to stop working, but the part they play is not one which enters actively into our consciousness, as do the muscles, nerves, and sense organs. ”

“ To illustrate, the word physiology, whether spoken or written, is in itself simply a sound or a visible symbol, but it stands for a highly complex group of associations in the human mind. In this respect language is a kind of shorthand.
It is hard to overestimate the importance of language to the human race. This is because of the enormous extension it gives to the ability to profit by experience. The lower animals are able to profit by experience, but the only experience that they can get is that which comes to them individually or to another animal which they may observe. ”

“ So far as experiment enables us to judge, the complete cessation of power development in cells, either of plants or animals, means their death.
Here we have our sign of life that is applicable to all kinds of cells wherever they are located, whether making up the whole of a microscopic animal or deeply imbedded in the body of a large animal which consists of millions of them. If power development is going on, the cell is alive; if no power is being developed, the cell is not alive. ”

“ What we really mean when we say that an animal is warm-blooded is that the temperature of its body runs about the same summer and winter, day in and day out. An animal that we call cold-blooded, on the other hand, cools down when in a cold place, but is warm when in a warm place. It therefore has a very variable temperature as compared with the almost constant temperature of warm-blooded animals. ”

“ The products from other kinds of organisms are poisonous to us, and when some of these organisms multiply within us we discover it, because we are poisoned and become ill. Only organisms whose products of metabolism are poisonous are counted ordinarily as causing infection. In the strict sense we might be said to be infected by the harmless organisms of which so many thrive within us, but in the usual use of the word we speak of one as having an infection only when his body has been invaded by organisms that produce poison. ”

“ Life is made up of bodily activities which may be carried on correctly or incorrectly. Carried on correctly they mean health, carried on incorrectly, unhealth. The world is flooded with health-preserving or health-restoring systems, urged upon the public, for the most part, by promoters in search of gain. Such of these as have merit are based on definite physiological principles, and anyone who has a common-sense working knowledge of his own body can order his life in accordance with them, at little or no expense. ”