HELEN: Which is best, to breathe through the nose or the mouth? MOTHER: Through the nose; for that was made for the air to pass through. Serious sickness of the throat and lungs is sometimes caused by breathing through the mouth. When the air goes this way, the person makes a very strange noise when asleep. The air seems to be trying to wake somebody up to shut the folding doors so it can go the right way. We call it snoring. PERCY: I should think when there are so many people and animals, and all must have air to breathe, that it would soon become unfit to use. MOTHER: We live in an ocean of air, as fishes live in the sea. The winds sweep it round and round, and everything that grows helps to make it pure. [Illustration: “_As fishes live in the sea._”] AMY: How can that be? MOTHER: It may be said that plants breathe, as well as people, only they need the poison gas we breathe out, and they give out the oxygen we need to breathe in. There is no danger but we can get all the air we need if we will let it into our rooms. ELMER: But isn’t night air bad to breathe, mother? MOTHER: No; for when it is night we can get nothing but night air. It is true that if air is shut up in a room it soon becomes unfit to breathe, whether it is night or day. PERCY: On frosty mornings my breath looks like steam as it comes out. Is that the poison gas, mother? MOTHER: No; we can not see the gas, but what you see is the water we breathe out. We take in about a pint of air at every breath, and it is said that every time we breathe out we spoil half a barrelful of air, making it unfit to breathe. I will let you find out how many barrelfuls of fresh air we would need in an hour. PERCY: Why, that would be over five hundred barrels! Who ever thought that we needed such a lot of fresh air in just one hour! MOTHER: And who, then, would think of using only one roomful in a whole night! It is no wonder that many people have a headache when they wake in the morning. HELEN: But, mother, we can’t get clean air always, even when we are not in the house. This very day a man puffed tobacco smoke into my face as I was passing him. AMY: But do you think it is _right_, mother, for any one to poison the pure, fresh air God has given us, with tobacco smoke, and make it unfit to use? MOTHER: No; I do not; and a true gentleman will not do it. It is both rude and wrong. He not only wrongs others but harms himself. You know how it feels to get smoke into your eyes, and it is just as bad for the throat and lungs. Bad smells of any kind poison the air, making it unfit to breathe, so we should be careful to keep our rooms and everything about the house sweet and clean. PERCY: I met a man in the street, and I could smell the whisky he had drunk. Did that come from his lungs?