We should all be as much against the breathing of impure air as we are against the drinking of dirty water and the eating of dirty food; but the air we breathe is, as a rule, far more impure than the water we drink or the food we eat. We are all worshippers of concrete objects; those things that can be seen and felt are regarded by us as of far greater importance than those which are invisible and intangible. Since air belongs to this latter class of objects, we fail to realise the evil wrought by the impure air that we breathe. We would think twice before eating the leavings of another man’s food, or drinking out of a cup polluted by another man’s lips. Even those who have not the least sense of shame or repugnance would never eat another man’s vomit, or drink the water which has been spat out by him; even those who are dying of hunger and thirst would refuse to do it. But, alas, how few of us realise that the air we inhale is so often the impure and poisonous air which has been exhaled by others, and which is surely no less objectionable than a man’s vomit! How strange that men should sit and sleep together for hours in closed rooms, and go on inhaling the deadly air exhaled by themselves and their companions! How fortunate for man that air should be so light and diffusive, and capable of penetrating the smallest holes! Even when the [Pg 17] 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, [Pg 18] while teaching their children also to do the same. I shall feel immensely gratified.