_Exercise_--At least twice a day an infant should be allowed for fifteen or twenty minutes the free use of its limbs by permitting it to lie upon a bed in a warm room, with all clothing except the shirt and diaper removed. In cold weather leave on the stockings. Later, when in short clothes, the baby may be put upon a thick blanket or quilt, laid upon the floor, and be allowed to tumble at will. _Rest_--Healthy children never sleep too much. A new born baby should sleep nine-tenths of the day. A child should have a nap during the day until four years old, and, if possible, until seven or eight years old. It should go to bed before six. It should have a crib or bed to itself, placed where it will have fresh air, but protected from draughts, and its eyes protected from direct rays of light. _Air and Sun_--A little child is in its room so much it is very important that fresh air and sunlight should be brought to it there. Rooms may be well aired twice or three times a day, removing the baby to another room while the windows are open. The child may be placed in its crib or carriage before on open window, dressed as if for the street. After children are three months old they may be taken out, but the sunny part of the day should be chosen, between 10 a. m. and 3 p. m. in cold weather. At night the windows should be partly opened, but care should be taken that the infant does not become chilled. Be careful that sheet and blankets do not get over a baby's head. The clothes may be pinned to the side of the bed. _Food and Water_--Even little babies should be given water twice a day. The water should be boiled, cooled and kept covered. It is hardly possible for children or older persons to drink too much water. During hot weather a child needs more water than during cold weather. Mother's milk is the only perfect food for an infant during the first nine or ten months. If it is necessary to give artificial food from a bottle, the greatest possible care must be taken. The milk used should be the best obtainable. To obtain clean milk it is necessary that everything that touches it be clean, sterilized when possible, and that the cows, and men who handle the milk be healthy. In New York City all milk is classified according to its cleanliness and butter fat content. The cleanest and richest milk is called "certified milk" and is sold raw. The other milks are classified according to cleanliness. Grade A, B and C are all pasteurized. Only certified and Grade A should be used for infant feeding. You know that sterile means free from germs or bacteria. Milk or water may be made comparatively sterile by boiling. Pasteurized milk is milk which has been heated to 155 deg. Fahrenheit, kept at that temperature for thirty minutes and cooled quickly by placing the bottles in cold running water.