Water

The struggles in life are largely struggles to satisfy part of our food requirements. The other part the slum dweller gets as easily as the owner of a Fifth Avenue mansion. That "other part" is water. Perhaps some day our food speculators will have studied the science of nutrition sufficiently to realize that water is as much a food as meat and butter and eggs; then they will tax their ingenuity to devise a means by which the production of this valuable liquid can be controlled, or its output restricted. But I must not put the speculator on this scent.

Abundant in quantity, and reaching the consumer at little or no cost, few of us ever include water in our list of foods; yet it is common knowledge that you can forgo eating longer than you can drinking. Water does not undergo any such changes in the digestive tract as do fats, proteins and carbohydrates; it is in fact absorbed and assimilated by the system without any change - like salt; and like the latter, yields no available energy. Its extreme importance arises from two facts: in the first place, a large percentage of living matter consists of water; secondly, the various phases of cellular activity require water as a medium. We are told that "all physiological actions have their seat in systems containing water as an essential element"; which, translated into our everyday language, means that life would be impossible without water. Thales, the ancient Greek philosopher, appreciated this when he formulated his system of philosophy in which water was made the origin of all things. Even our good friend Aristotle made water one of the cardinal points of his system of the universe. It is only in our own day that our indifference to the liquid has become so apparent, and that in place of it we have come to worship the cocktail, which, nevertheless, may contain over 90 per cent of water.

Our water requirement we get in several ways. Plebeians get it largely from water direct. Almost all of us get some, and many of us get most of our water from beverages. But all of our solid foods contain water. Some, such as fruit and many vegetables, may contain as much as 80 to 90 per cent of the liquid. That is why the calorific expert claims that you do not get your money's worth by eating fruits and vegetables. Our later chapters will show that the calorific expert will need to revise some of his opinions.

Oxygen

In our discussion of calories, we emphasized that our source of energy arises from the burning (or combustion, or oxidation) of foods in our system. This burning, as was pointed out, is impossible without the presence of oxygen (or air, which contains oxygen), just as oxygen is needed to burn a candle.

If by a food we mean a substance which supplies or helps to supply energy, or one which repairs the waste of tissues and provides raw material for growth, or a substance which serves both these functions, then oxygen is most certainly a food. Absorbed by the lungs from the air and taken up by the red blood cells in the blood, the oxygen is distributed to the cells of the body, and there the oxidations take place.

The consequences of a lack of oxygen supply are soon apparent. Sometimes the individual may be surrounded by plenty of air, but his bodily machinery may be in such poor condition that he finds it difficult to assimilate the necessary supply. The disease known as asthma may serve as an example. Sometimes again the supply of air may be limited. Again a gas may be present in the air of which the red blood cells may be fonder than of oxygen. Cases of asphyxiation come under this heading. Here one of the products of the incomplete burning of coal in the stove, carbon monoxide, fills the room and finally enters our blood, which seems to have a greater "affinity" for it than for oxygen. But carbon monoxide cannot substitute for oxygen in the burning of foods; so death results.

"Fresh" Air

Since the need for "air" is primarily our need for oxygen, the question arises, why the desire for fresh air? Does such air contain more oxygen than the air of a well-ventilated room? That cannot be, for the percentage of oxygen in each is the same. Have the other constituents of the air an influence? No doubt, but the most careful chemical and bacteriological analysis fails to distinguish the air outside from the air in a well-ventilated apartment. "A partial explanation" [of the obviously beneficial effects of fresh air], writes Professor Bayliss, "may be, as Leonard Hill contends, that the effect [in a room] is due to the absence of currents of air and the stimulation of the skin produced by them. It would thus be a result of failure of stimulation of the nervous system. The general experience of more refreshing sleep obtained when the bedroom window is open tends to support the view of the importance of the effect on the nervous system. The benefit of a 'cold bath' is probably of a similar nature, as is also that of 'exercise' to a certain extent."