Pure air soothes the nerves, circulates the blood healthily through the system, refreshes the body and mind, excites the appetite, renders better digestion and induces sound sleep.

However, ill-ventilated rooms weaken the system, depresses circulation and the mind, and may produce colds. It is close confinement indoors that makes many feeble and pale. They breathe the same air over and over, until it becomes laden with poisonous matter thrown off through the lungs and pores; and impurities are thus conveyed back to the blood.