In discussing the question of health, we have given the greater part of the space to the subject of diet, for the reason that experience has convinced us that diet is two-thirds of health, and that nearly always in disease you find errors of diet playing a part. There are, however, other important factors of health, now to be discussed.

Everything of which the body makes use is taken in the form of food and drink, with the exception of one substance, the oxygen we get out of the air. Every time we draw a breath we take in a certain amount of oxygen, and every time we expel a breath, we drive out a certain amount of a gas called carbon dioxide, which is what the body makes of the fuel it burns. The body can get along for several days without water, and for two or three months without food, but it can only get along for two or three minutes without oxygen. It should be obvious that when the body expels carbon dioxide, with a slight mixture of other more poisonous gases, and sucks back what it expects will be a fresh supply of oxygen, it wants to get oxygen, and not the same gases it has just expelled, nor gases which have been expelled from the lungs of other people.

In the days when primitive man lived outdoors, he did not have to think about this problem. When he breathed poison from his lungs, the moving air of nature blew it away, and the infinite vegetation of nature took the carbon dioxide and turned it back into oxygen. And even when man built himself shelters, he was not cunning enough to make them air-tight; he had to leave a big hole for the smoke to get out, and smaller holes through which to get light. But now our wonderful civilization has solved these problems; we make our walls of air-tight plaster, and we have invented a substance which will admit light without admitting air. So we have the "white plague" of tuberculosis, and so we have innumerable minor plagues of coughs and colds and sore throats.

In the summer time the solution of the problem is easy. Have as many doors and windows in your home as possible, and keep them open, and have nothing in your home to make dust or to retain dust. But then comes stormy and cold weather, and you have to close your doors and windows, and keep your home at a higher temperature than the air outside. How shall you do this, and at the same time get a continual supply of fresh air?

I will take the various methods of heating one by one. The problem in each case is simple and can be made clear in a sentence or two.

First, the open fireplace. This is a perfect solution, if you have enough fuel, and do not have to worry about the waste of heat. An open fireplace draws out all the air in the room in a short time, and you do not have to bother about opening doors or windows; you may be sure that the air is getting in through some cracks, or else the fire would not burn.

Second, a wood or coal or gas stove in the room, provided with a proper vent, so that all the gases of combustion are drawn up the chimney. This changes the air more slowly than an open fireplace, but it does the work fairly well. All that you have to be careful about is that your vent is sufficiently large and is working properly. If your fire does not "draw," you will have smoke or coal-gas in the house, and this is bad for the lungs; but worse for the lungs is a gas that you can neither see nor smell nor taste, the deadly carbon monoxide. This gas is produced by incomplete combustion, and whenever you see yellow flames from gas or coal, you are apt to have this poisonous substance. Small quantities of it are sufficient to cause violent headaches, and repeated doses of it are fatal. Men who work in garages which are not properly ventilated run this risk all the time, because carbon monoxide is one of the products of imperfect combustion in the gas engine.

Next, the furnace. A furnace sends fresh warm air into your house; the only trouble is that it takes out all the moisture, and some authorities say that this is bad for the lungs and throat. I do not know whether this is true, but all furnaces are supposed to have a water chamber to supply moisture to the air, and you should keep a pan of water on every stove or radiator in your house.

Next, steam heat, which includes hot-water heating. This is one of the abominations of our civilization, and one of the methods by which our race is committing suicide. There is nothing wrong about steam heat in itself; the room is warmed in a harmless way; but the trouble is it stays warm only so long as the doors and windows are kept shut. You are in an air-tight box, and can be warm provided you do not mind being suffocated. The moment you open a door or window, you have a cold draft on your feet, and if you wish to change the air entirely you have to let out all the heat; so, of course, you never do change it entirely, but go on breathing the same air over and over, and every time you breathe it the condition of your body is a little more reduced.

The solution of this problem is not to heat the air in the room, but to use your steam coils to heat fresh air, and then drive this air, already warmed, into the room, at the same time providing a vent through which the old air can be pushed out. This is the hot air system of heating, and it requires some kind of engine or dynamo, and therefore is expensive. It has been installed in a few office buildings and theaters. One of the most perfect systems I ever inspected is in the building of the New York Stock Exchange, where the air is warmed in winter, and cooled in summer, and freed from dust, and exactly the right quantity is supplied. It is a humorous commentary upon our civilization that we take perfect care of the breathing apparatus of our stock-gamblers, but pay no attention to the breathing apparatus of our senators and congressmen, whose one business in life is to use their lungs. The stately old building with its white marble domes looks impressive in moving pictures and on illustrated postcards, but it has no system of ventilation whatever, and is a death-trap to the poor wretches who are compelled to spend their days, and sometimes their nights, within its walls. This contrast is one symptom of the rise of industrial capitalism and the collapse of political democracy.

We have reserved to the last a method of heating which is the worst, and can only be described as a crime against health: the use of gas and oil stoves set out in the middle of the room, without a vent, and discharging their fumes into the room. These stoves are simply instruments of slow death, and their manufacture should be prohibited by law. In the meantime, what you have to do is to refuse to live in a room or to work in an office where such stoves are used. I have heard dealers insist that this or the other kind of gas or oil stove was so contrived as to consume all the fumes. Do not let anybody fool you with such nonsense. There has never been any form of combustion devised which consumes all the fumes. No such thing can be, because the products of combustion are not combustible. The so-called "wickless blue flame" stoves do burn all the oil, and a properly regulated gas stove will burn all the gas, but that simply means that it turns the oil and gas into carbon dioxide, the very substance which your lungs are working day and night to get out of your body.

Moreover, there is no oil or gas stove which ever burns perfectly all the time, either because there is too much gas or insufficient air. Oil and gas stoves sometimes give a partly yellow flame. You can cause them to give a yellow flame at any time by blowing air against them, and that yellow flame means imperfect combustion, and a probability of the deadly carbon monoxide. These facts are known to every chemist and to every student of hygiene, and the fact that civilized people continue to burn such oil and gas stoves in their homes and offices is simply one more proof that our civilization values human welfare and health at nothing whatever in comparison with profits.

Not merely should you see that you have a continuous supply of fresh air in your home, but you should try to keep down dust in your home, and especially fine particles of lint. Once upon a time our ancestors were unable to make houses and floors tight, and so they put rugs on the floors and hung tapestries on the walls to keep out the wind. We civilized people are able to make both floors and walls absolutely tight, and yet we continue to use rugs and curtains, it being the first principle of our education that propriety requires us to continue to do the things which our ancestors did. I am unable to think of a more silly or stupid thing in the world than a rug or a curtain, but I have lived in the house with them all my life, because, alas, the ladies cannot be happy otherwise. They want their homes to be "pretty," and so they continue to set dust traps, and to set themselves futile jobs of house cleaning and shopping.

Not all of us are able to be out of doors as much as we ought to be, but all of us spend seven or eight hours out of every twenty-four in sleep, and this time at least we ought to spend out of doors. I understand that this is futile advice to give to the very poor. I was poor myself for many years, and had to put all my clothes on at night in order to keep warm, and even then I could not always do it. Nevertheless, from the time I first realized the importance of ventilation I never slept in a room with a closed window.

I say, sleep outdoors if you possibly can. You do not have to be afraid of exposure, for cold will not hurt you if you keep your body in proper condition. I have slept out in a rubber blanket, with the rain beating on my head and face; I have spread a rubber blanket on a hummock in the midst of a swamp, and waked up in the morning with my hair and face soaked in cold, white fog, but I never caught cold from such things; there is no harm whatever in dampness or in "night air," if you are in proper condition. Of course, you may get your ears frostbitten in the middle of winter, but you can have a sleeping hood to remove that danger.

The "nature cure" enthusiasts, who lay so much stress upon an outdoor life, also insist that the wearing of clothes is a harmful civilized custom. They urge us to take "sun baths" and to "ventilate the skin." Now, as a matter of fact, the skin does not breathe, it merely gives out moisture, and it does not give out any less because we have clothing on us, provided the clothing is dry and clean, and will absorb moisture. But bye and bye the clothing becomes loaded with the waste substances given out by the skin, and then it will absorb no more, and if you do not change your clothing, no doubt it may have some effect upon health.

But the principal evil of civilized clothing is that it binds the body and prevents the free play of the muscles, and, more important yet, stops the free circulation of the blood. I have already discussed hats, which are the principal cause of baldness. I will go to the other extremity of the body, and mention tight shoes, which, strange as it may seem, cause headaches and colds. You will be able to find a few civilized men with normal feet, but you will hardly ever find a woman whose toes are not crowded together and misshapen. I have said that the human body is one organism, and that it is fed and its health maintained by the blood-stream; I say now that the circulation of the blood is one thing, and if you block it at any one place, you block it everywhere. Of course, not all the blood-stream goes down into the feet, but some of it does, and if it is clogged in the feet, and the blood vessels cramped and crowded, there is a certain amount of poison kept in the system, which the system should have got rid of.

Why do women wear tight shoes? Because the leisure class members of their sex have been kept in harems and used as the playthings of men. To be fragile and delicate was the thing admired by the masters of wealth, and to have small hands and feet was a sign that women belonged to this parasite class. Therefore at all hazards women's feet must be kept small, even at the expense of their health and happiness; and so they put themselves up on several inches of heels, which cause them to toddle around like marionettes on a stage, with all their toes crowded down into a lump.

Why do men wear tight bands around their scalps, which cause their hair to drop out, and tight, stiff columns around their necks, which stop the circulation of the blood into their heads, and cause them to have headaches instead of ideas? The reason is that for ages the rulers of the tribe have wished to demonstrate publicly their superiority to the common herd, which does the menial tasks. In England all gentlemen wear tall black silk band-boxes on their heads, and in America they have a choice among several varieties of round tight boxes. All men who work in offices wear stiffly starched collars and cuffs, as a means of demonstrating their superiority to the common workers, who have to sweat at their necks. I think it is not too much to hope that when class exploitation is done away with, we shall also get rid of these class symbols, and choose our clothing because it is warm and comfortable, and not according to the perverted imbecilities of "style."

The skin gives out perspiration which is greasy; also the skin is constantly growing, putting out layers of cells which dry up and are worn off. We need to bathe with soap to remove the grease, and we need to rub with a towel to brush away the dead cells of the skin, so that the pores may be kept open. No one is taking care of his body who does not wash and rub it once every twenty-four hours, and once or twice a week with warm water and soap. It is often stated that hot baths are weakening, but I have never found it so; however, I think it is a bad practice to pamper the body, which should be accustomed to the shock of cold water. The rule as to bathing, both as to temperature and time, is simple. If, after the bath and rub-down, your body has reacted and you feel vigorous and fresh, that bath has done you good. If, on the other hand, you feel chilled and depressed, then you have been too long in the water, or its temperature was too low. Every person has to find his own rules in such matters. The only general rule is that as one grows older the body reacts less quickly.

All day, as we work and think, we store up more poisons in our cells than the body can get rid of, and the time comes when the cells are so loaded with poisons that we have to stop for a while, and let our blood-stream clean house. The quantity of sleep one needs is a problem like that of cold water; each person has to find his own rule. In general, one needs less and less sleep as one grows older. Infants sleep the greater part of the time; growing children should sleep ten or eleven hours, adults seven or eight, and old people, unless they have let themselves get fat, generally do not want to sleep more than six, and part of this in short naps. When you sleep, your bodily energies relax, and you make less heat, therefore you need extra clothing; but this clothing should never cover the mouth and nose, nor should it be so heavy as to make breathing a burden. If you are in good condition, it will do you no harm to be chilly when you sleep, except that you do not sleep so soundly. Sleeping too much is just as harmful as sleeping too little. Nature will tell you that. The important thing, as in all other problems of health, is to have something interesting to think about, some exciting work to do in the world, and then you will sleep as little as you have too.