Essentials of Life.—Air, water, and food are the great essentials of life. A man may go for days without food, and for hours without water, but deprive him of air, even for a few minutes, and he ceases to live. In quantity, the daily consumption of air far outmeasures the other two; in purity, it receives the least consideration. The city and the State alike exercise some oversight of the food and water supply of the people. Impurities in these often appeal to the sense of sight or smell or taste, and the individual is put on his guard. The intangible air is laden with the foulest and most poisonous substances, and is as freely inhaled as if it could make no difference to the health.

Lung Capacity.—The quantity of the air we breathe is also important. We may eat too much food, even though it be absolutely pure and wholesome, but we cannot consume too much pure air. The larger the lung space, therefore, the better for health and strength.

The full lung capacity of the average adult is about 330 cubic inches, but an ordinary inspiration does not take in more than one-eleventh part of that volume. The value of full, deep breathing, and of large lung capacity becomes at once apparent. The larger the quantity of air consumed, the greater the amount of life-giving oxygen conveyed through the blood to all parts of the body. No form of physical exercise, therefore, can exceed in value the breathing exercises described in another chapter.

Rate of Breathing.—It is estimated that we breathe once during every four beats of the heart, or about eighteen times a minute. The relation between the heart and lungs is so close that whatever modifies the pulse affects the breathing. When the heart action is hurried, more blood is sent to the lungs, requiring more rapid action on their part. About every fifth breath the inspiration is longer and fuller, the effect being to change more completely the air of the lungs.

Holding the Breath.—While respiration is, for the most part, involuntary, we may arrest the breathing for the space of twenty to thirty seconds. If we first fortify the lungs by taking several deep inspirations and expelling the impure air as fully as possible, we may hold the breath for a minute or two. This power will prove of advantage if we have occasion to pass through a room or hallway filled with smoke, or to remain under water for a brief time. The pearl-fishers, as a result of training, remain under water from three to four minutes.

Importance of Pure Air.—Pure air means pure blood. The air of the mountain tops or by the sea fills us with life, while that of narrow streets, crowded rooms, unventilated dwellings, schools, churches, and theatres is depressing, weakening, and death-dealing.

So far from the aristocracy having a monopoly of blue blood, it flows through the veins of high and low alike. It goes out from the lungs bright and rich with oxygen; it comes back to the heart dark with the waste and poisonous matters which it has gathered in its course.

Atmospheric air is composed of several gases, the principal elements being oxygen, nitrogen, and watery vapor. All animal life requires oxygen for the combustion of the material supplied through the blood. The blood makes its circuit through the body three times a minute. It comes to the lungs laden with poisonous matter. Nearly one-third of the excretions of the body are eliminated through the lungs. The average adult contaminates about five thousand cubic inches of air with every breath. The importance of having an abundant supply of pure air at all times is obvious.

In ordinary respiration an adult abstracts sixteen cubic feet of oxygen from the atmosphere every twenty-four hours, and adds to it fourteen cubic feet of carbonic acid in the same time. If the individual were confined in a close apartment, in which the air could not mingle with the atmosphere without, the processes of life could not long be maintained.

History furnishes many instances of the direful effects of crowding a number of human beings into a limited space without ventilation. One hundred and fifty passengers were confined in the small cabin of a steamship one stormy night, and when morning came only eighty were found alive. Three hundred prisoners, after the battle of Austerlitz, were crowded into a close prison, and within a few hours two hundred and sixty of them had died.

The effects of foul air are not usually so sudden nor so striking. More frequently they consist of a general deficiency of nutrition, loss of vigor of body and mind, and of the power of resistance to disease. Consumptive patients, in a large majority of cases, come from the classes whose occupations confine them to ill-ventilated rooms. A cramped position of the body while at work, and want of good wholesome food, contribute to the mortality from this cause.

Absolutely pure air is rarely found in nature. Even in the open country there are three parts of carbonic acid in ten thousand parts of air. In cities and towns, the out-door air contains from four to five parts of carbonic acid. When, in dwellings and churches and halls, it reaches six to seven parts, its impurity is detected by the nose, the lungs suffer from a lack of oxygen, and the room feels close and stuffy.

The amount of carbonic acid in the breath is about five per cent. Air once used is therefore unfit for purposes of animal combustion. If breathed into a jar containing a short lighted candle, it will at once extinguish the flame. It would also prove fatal to small birds or mice. When the carbonic acid reaches one part in ten of common air, it becomes fatal to man.

Headaches, dullness, drowsiness, and labored respiration are the first symptoms of this lung poison. Faintness, convulsions, and unconsciousness are a later stage. School-houses, churches, theatres, and factories should be so well ventilated that the proportion of carbonic acid would not exceed two parts in one thousand.

Effects of Breathing Impure Air.—Air which is only slightly vitiated, if breathed day after day, for a considerable time, produces most serious results. Its effects are seen in pale faces, loss of appetite, depressed spirits, and a lack of muscular vigor.

An investigation made some years ago showed 86 deaths per 1,000 in a badly ventilated prison, and of these, 51.4 per 1,000 were due to phthisis, or consumption. In the House of Correction, in the same city, which was well ventilated, the death rate was 14 per 1,000, and of these only 7.9 were occasioned by phthisis. The organic particles thrown off from the lungs of diseased persons are responsible for the prevalence of phthisis and other lung diseases. It is also a well established fact that a bad atmosphere promotes the rapid spread of such specific diseases as small-pox, typhus, and scarlet fever.

Constant Supply.—Of so great importance is the matter of having a constant supply of unvitiated air that sanitariums for consumptives are now becoming common in which the principal feature is to have the patients enjoy a continuous out-door existence, day and night, being wrapped up and otherwise protected from cold and dampness. Consumptive symptoms often yield to this treatment.

Individual Habit.—Habit has much to do with our appreciation of pure air. If we recognize its value to health and to all the mental and physical activities, and insist upon a plentiful supply of pure oxygen, the habit soon becomes a second nature, and we instinctively feel uncomfortable upon entering an ill-ventilated room. In northern climates, economic considerations often interfere with the highest sanitary regulations. Householders, school boards, and church trustees frequently save fuel at the expense of health.

We may, however, by spending much time in poorly ventilated rooms, become so accustomed to the depressing influence of the impoverished atmosphere that we suffer a sort of semi-stupor without being conscious of the fact. How great a wrong is inflicted upon children in the school-room and in the crowded factory, by subjecting them, day after day, for months and years, to a vitiated atmosphere, laden with the poisonous exhalations from lungs and skin! Their growing bodies are stunted and their awakening intellects dulled, and the seeds of disease and weakness are implanted to develop into a harvest of wretchedness and misery in later life.

Sea Air.—When the breeze is off the ocean, the air is practically free from the exhalations of animals, the smoke and soot of chimneys, and the gases of sewers. The curative value of sea-air is well known. It comes richly laden with ozone, and its effect upon sojourners at the sea-side is very stimulating. Many persons are not strong enough to endure sea-bathing, yet gain much benefit from the sea-air.

Mountain Air.—The air of the mountains is pure. It is usually still, and seldom foggy. Being more rarefied than that of the low-lying valleys, it contains less oxygen in proportion to volume, but its lesser density gives to the oxygen greater activity.

The body loses heat less rapidly in rarefied atmospheres, so that there is probably less need of heat-production on the mountain than on the plain, combustion being less active. The rapid and great variations of temperature of the mountain regions stimulate the vital processes and contribute to the curative agencies of those altitudes.

Night Air.—There is a prevailing prejudice against night air. By many persons out-door air is shut out of the sleeping room as if it were pestilential. Analysis as well as experience shows that the most vitiated and unwholesome night air is that which has been breathed over and over again in a close sleeping apartment. Admit the outside air freely if you desire health. Guard against draughts, and use just enough bed covering for comfort.

Air of the School-Room.—A plentiful supply of pure air is desirable wherever there are people to breathe it. In no place is it more important than in the school-room. Confined for six hours each day during the period of life when the best health conditions are required for the proper growth of mind and body, the child thus robbed of the needed oxygen is wronged. The adult who voluntarily subjects himself once or twice a week for two hours to the poisonous atmosphere of church, lecture hall, or theatre, may experience a temporary headache, but is soon revived after reaching the fresh air. The child, ignorant of the wrong he is made to suffer, and incapable of providing better conditions, breathes the poisonous exhalations from fifty pairs of lungs, day after day, and thus has sown in his system the seeds of disease.

Illuminating Gas.—Many persons die every year by inhaling illuminating gas. People unacquainted with the use of gas fixtures often blow out the light instead of turning the key. A prevailing custom in some families is to keep the light burning low during the night. A variation of pressure in the pipes, or a sudden draught of air, extinguishes the slender flame, and gas escapes into the room, often with fatal results.

Leaky pipes or faulty fixtures may have the same effect. If the key be loose, tighten the screw that holds it in place. If there is a leak in the pipe or joint, which may be determined by applying a match, a gas-fitter should at once be summoned. Delay is dangerous and may prove fatal.

If a room be heavily charged with gas, get the windows and doors open as soon as possible. Do not go near with a light, lest an explosion follow. Naphtha and benzine are also highly explosive. When either is used to clean clothing, the work should be done in the open air, and never where the fumes may come in contact with the fire of stove or range, or with the flame of candle or lamp.

Gas burners, oil lamps, sperm candles, all forms of illuminants, consume the oxygen of a room and increase the carbonic acid. An oil lamp of ordinary dimensions gives off as much carbonic acid as an adult person. A man, seated in a room of moderate dimensions and using a good oil lamp, will require 6,000 cubic feet of fresh air every hour in order to keep the air from becoming vitiated beyond the point of wholesomeness. Gas from coal, coke, or charcoal fires is as dangerous as illuminating gas.

Heaters, ranges, stoves, and furnaces should be kept in complete order, so that no gas shall escape. Its entrance into a bedroom is often so stealthy as to stupefy the unconscious sleeper and destroy life without awakening him.

Sewer Gas.—Of all forms of vitiated air in cities, none is responsible for such serious derangement of health as that which is polluted by the air or gas from sewers and waste pipes. Some physicians and sanitarians hold that sewer air is often the direct cause of typhoid fever, scarlet fever, diphtheria, and cholera. Others maintain that the sewers and pipes furnish favorable breeding places for the germs of these diseases, which germs are carried through the air and produce their effects. The important matter is to keep the waste pipes flushed and well trapped. Some precautions against sewer gas are treated in the chapter on Dwellings.

Influence of Climate and Temperature.—Diarrhoeal diseases, both of adults and children, are most frequent during hot weather. In July, August, and September there are from ten to twelve times as many cases as at other seasons of the year. Proper diet and suitable clothing will go far toward protecting the individual from the ill effects of climate and season.

The mortality from consumption and other forms of lung diseases is greatest in March and April, and least in August and September. September and October claim the greatest number of deaths from typhoid fever, followed closely by August and November. The mortality from diphtheria and croup is highest in November and December, and lowest in August and September. Of suicides, the largest number occur in May, and the fewest in February.

Hygienic Value of Winds.—Prof. Dexter, of the University of Illinois, has made a careful study of the effects of calms on the records of the public schools, the police courts, and the penitentiaries. All air movements not exceeding four miles an hour are regarded as calms. Over 497,000 observations were considered and tabulated. These show that during calm weather the absence from school on account of illness is three times as great as that during all other kinds of weather, including the very cold, wet, and windy. During calms, the criminal records show less disorder and violence, more policemen are laid off, more errors are made by clerks in banks, and more deaths are reported. This is in accordance with the principle that oxygen is the great source of mental and physical energy. When oxygen is deficient, we are less capable of action, either for good or evil. The slowly-moving air-currents of a large city are robbed of their oxygen, and vitiated by the exhalations of thousands of men and animals. A brisk wind brings in a fresh supply of vitalized air to take the place of the old, and to promote physical and mental energy. Old Boreas is a better friend than we have been wont to believe.

Nature’s Balance.—By a wise provision of nature, the carbonic acid, which is so destructive to all animal life, constitutes the chief food of plants. These absorb the carbon and give out oxygen, and in this way the animal and vegetable kingdoms tend to preserve the balance of nature. Except for this wonderful provision, the human family would be threatened with annihilation.

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