=Exercise.= Exercise, as either work or play, is necessary because it stimulates the action of all the organs of the body. The blood circulates more freely during exercise, and more waste products are thrown off. One should not take violent exercise immediately after eating; neither should one exercise when unduly fatigued. Work must be wisely alternated with play and rest, because efficiency ends when a person becomes overtired. CHAPTER II HOME SANITATION =Suggestions for demonstrations.= =1.= Demonstrate the ventilation of a room. =2.= Demonstrate the dusting of a room. By home sanitation we mean keeping the house clean and giving the forces of nature, such as sunshine, fresh air, and pure water, their fullest opportunity to work for us. By letting the out of doors indoors we give nature a fairer chance at her great task of keeping us well and happy. The house is a protection for the family and should have healthful and cheerful surroundings. The housewife should understand the principles of home sanitation and thereby secure for her family a healthy and happy life. =Location of the house.= The location of the house is often decided more by necessity or convenience than by the consideration of health. If possible, a tenement or house should be so situated as to secure good air, sunshine, good drainage, and good neighbors. A house with a southerly exposure or placed with its corners to the points of the compass has a distinct hygienic value and is always to be preferred, because it gets the sun in each room at some time during the day. =Sunshine.= Abundant sunshine and light in the home are of great importance, and help to make the home healthful and more cheerful. People living in rooms which have no sun become pale and gradually lose strength. =Pure air.= Sunshine and pure air are the most important essentials for healthy life in the home. Nothing will take the place of fresh air. Everyone should be taught to fill the lungs with it by slow, deep breathing. We breathe on an average eighteen times a minute, or 25,920 times every twenty-four hours. No matter how well rooms are ventilated, it is a good plan to open the windows wide a few times each day. This helps to rid the atmosphere of impurities. =Oxygen.= Oxygen is the element in the air that sustains life; it is inhaled through the lungs, taken up by the blood, and carried to all parts of the body. =Carbon dioxide.= The air also contains carbon dioxide, which is a product of combustion in many forms, such as respiration and the decomposition of animal and vegetable matter. Although enormous quantities of carbon dioxide are constantly being forced into the air, it is likewise being removed constantly—especially by growing vegetation. Plants and trees, under the influence of sunlight, absorb much of the carbon dioxide; therefore plants, which many people like to have in their rooms, not only please the eye but have a practical value.