doors and windows are closed, there is generally some little space between the walls and the roof, through which some air from outside manages to get in, so that the inmates of the room have not to breathe exclusively poisoned air. The air that we exhale mixes with the air outside, and is rendered pure again by an automatic process that is always going on in Nature.
Now we are able to understand why so many men and women should be weak and diseased. There can be absolutely no doubt that impure air is the root-cause of disease in ninety-nine cases out of every hundred. It follows that the best way of avoiding disease is to live and work in the open air. No doctor can compete with fresh air in this matter. Consumption is caused by the decay of the lungs, due to the inhaling of impure air, just as a steam engine which is filled with bad coal gets out of order. Hence doctors say that the easiest and the most effective treatment for a consumptive patient is to keep him in fresh air for all the 24 hours of the day.
It is, of course, essential to know how we can keep the air pure. In fact, every child should be taught the value of fresh air, as soon as it is able to understand anything. If my readers would take the trouble to learn the simple facts about the air and would put their knowledge into practice,