By means of the mind we feel, and know, and think. The mind uses each part of the brain for only one kind of work. =142. The senses.=--The cells of the body send word to the brain over the nerves. The eye tells of sight, the ear of sounds, the nose of odors, the mouth of tastes, and the skin of feelings. All these messages go to the back part of the brain. They tell the mind of the news outside of the body. We get all our knowledge in this way. The cells also tell of their need of food and drink by means of the feelings of hunger and thirst. =143. Motion.=--The mind in the cells of the top part of the head sends the orders for moving the different parts of the body. When we wish to run, the mind in the top of our head sends an order over our nerves to our legs, and they carry the body where we wish. If the top part of your brain is hurt, as by a blow, it cannot send orders to move, but you will lie stunned. =144. Memory.=--The mind lays away all its messages, and often looks them over again. These old messages are called _memories_. They always stay with the brain, and the mind can call them up at any time. Our memories make our knowledge. Every act of the mind leaves some mark on the memory. We may not be able to bring it back when we want to, but it will come back some time. Every bad word and evil deed will tend to come back and make us bad again. Every good work and word will leave its memory and make us better. We ought to fill our minds with good memories. =145. Thinking.=--The brain also thinks. Thinking is different from feeling and from moving, but we can think about our feelings and about our movements. The brain just back of the forehead does all our thinking. A dog has only a little forehead, and cannot think much. But the rest of its brain is large, for it can see and hear and run as well as a man. A baby can see and hear and move, but it cannot think until it is taught how. Boys and girls go to school to learn to think. Thinking is work, just as truly as running is work. At school, no one can learn to think without working. Looking at things and hearing some one talk about them will not make you a strong-minded man, but thinking about these things will. Boys and girls should study and think, as well as look around and listen.