=177. Smell.=--We smell with the nose. Some things give out a vapor to the air. When we draw the air into the nose, this vapor touches the nerves, and we perceive a smell. The nerves are high up in the nose. In order to perceive smell clearly, we sniff the air far up the nose. =178. Use of smell.=--Bad air and spoiled food smell bad. A bad smell is the sign of something spoiled. The sense of smell tells us when food or air is unfit for use. Some people try to hide a bad smell with perfumery. To do this only makes the danger greater, for then the smell does not tell us of the danger of food or air. Some animals can smell much better than a man. A dog will smell the track of a wild animal hours after it is made. Savages can smell much better than civilized men. =179. Taste.=--We taste with the tongue. Dry food has no taste, but it must first dissolve in the mouth. Spoiled food tastes bad. Bad-tasting food is not fit to eat. Taste tells us whether food is good or bad. We can learn to like the taste of harmful things. At first no one likes tobacco or strong drink, but the liking is formed the more one uses these. We ought to be careful not to begin to use such things. _Alcohol_ and _tobacco_ burn the mouth and harm the taste. Food does not taste so good and we may eat spoiled food and not know it. WHAT WE HAVE LEARNED 1. We can feel in every part of the body, but mostly in the ends of the fingers. 2. Light makes a picture upon the nerves inside of the eye. 3. If the eyes ache, the light should be softened or the position of the book or work changed, or else the eyes should be rested. 4. Sound in the air goes into the ear and strikes against a drum. Bones then carry the sound to the ear nerves. 5. Air snuffed up the nose gives the sense of smell. Smell tells us if the air or food is fit for use. 6. Taste tells us whether food is fit for use. Men can learn to like the taste of wrong things like tobacco or alcohol. [Illustration: =The Human Skeleton, showing position of bones.=] CHAPTER XIV BONES AND JOINTS =180.= Bones make the body stiff and strong, and give it shape. Long bones reach through the arms and legs, and little bones reach down the fingers and toes. Rounded plates of bone form the head, and a pile of bony rings makes up the backbone. Each bone is built to fit exactly into its own place and to do its own work. In all there are over two hundred bones in the body. They form one seventh of its weight. =181. Form of bones.=--A bone is not like a solid piece of timber, but is hollow like the frame of a bicycle. This makes it strong and light. At its ends a bone is like a hard sponge covered with a firm shell. This makes it too strong to be easily crushed, and keeps it light.