=3. What cells do.=--Each cell acts much as an ameba does. From the blood it gets food and air and takes them in through any part of its body. It also grows and moves. But the cells are not free to do as they wish, for they are all tied together in armies by very fine strings. We call these strings _connective tissue_. One army of cells makes the skin, and other armies make the bones and flesh. Some armies make the fingers, and some the legs. Every part of our body is made up of armies of separate cells. =4. The mind.=--The body is a home for the mind. The cells obey the mind. The mind pays the cells by feeding them and taking good care of them. When an army of cells is hurt, the body feels sick, and then the mind tells the whole body to rest until the cells are well again. When we study about a man's body, we learn about the separate cells in his body. WHAT WE HAVE LEARNED 1. Our body is made up of many small parts. 2. The smallest parts are each like a little animal, and are called _cells_. 3. Each cell eats and grows. 4. One army of cells makes a finger and another a leg, and so on through the body. 5. The mind lives in the body. 6. The mind takes care of the cells. CHAPTER II OF WHAT CELLS ARE MADE The cells of our body are made of five common things. You would know all these things if you should see them. =5. Water.=--The first thing in the cells is _water_. Water is everywhere in the body. Even the teeth have water. Most of our flesh is water. Without water we should soon shrink up. Our flesh would be stiff like bone and no one could live. [Illustration: =The body is made of these five things.=] [Illustration: =Fat tissue (×100).= The liquid fat is stored in living pockets.] =6. Albumin.=--_Second_, next to water, something like the white of an egg makes the most of the body. The white of an egg is _albumin_. When dried it is like gelatine or glue. Albumin makes the most of the solid part of each cell. Lean meat and cheese are nearly all albumin. When it is heated it becomes harder and turns white. The word albumin means white. Dry albumin is hard and tough, but in the living cells it is dissolved in water and is soft like meat. It is the only living substance in the body, and it alone gives it strength. =7. Fat.=--_Third_, next to albumin, the most of the body is fat. Fat does not grow inside the cells of the body, but it fills little pockets between the cells. Fat does not give strength. It makes the body round and handsome. It also makes the cells warm and keeps them from getting hurt. =8. Sugar.=--_Fourth_, sugar also is found in the body. Sugar is made out of starch. When we eat starch it changes to sugar. Starch and sugar are much alike. We eat a great deal of starch and sugar, but they are soon used in warming the body. Only a little is in the body at once.