AMY: And it has roots, which hold it fast in the ground. MOTHER: Yes, trees are made to stand in one place while they live, and so they have roots. We have limbs like the tree, but our lower limbs are used to carry us from place to place, for we were not made to stand still. Can you think of another way in which we are like the tree? HELEN: Oh, I know! The middle part of the body is called the trunk. MOTHER: Can you think of any other kind of trunk than the trunk of a tree or the trunk of the body? AMY: A trunk in which to put clothes. [Illustration: A trunk] MOTHER: Yes, such trunks are useful to carry clothes. The upper part of the trunk of the body, or the part between the arms, is called “the chest.” Sometime we will try to learn what is packed away so nicely in the chest, or trunk, of the body, but we will only look outside now. What is on top of the trunk? HELEN: A strong, shell-shaped box made of bones, called the head. MOTHER: This is what we might call the jewel-case, or the best part of all, for without it all parts of the body would be useless. Here we find the eyes, nose, mouth, and ears; and the head is fastened to the trunk of the body by the neck. How many limbs have we? PERCY: We have two arms and two legs, and these are called our limbs. MOTHER: Now I think you can name the main parts of the body. What are they? HELEN: The head, trunk, and limbs. MOTHER: You said the tree was covered with bark. Look at your hand. With what is it covered? AMY: With skin. MOTHER: Yes; we will talk more about this soft covering of the body at another time. We found these body-houses of ours are made to walk, work, run, jump, and do many other things. How are our limbs different from those of a tree? PERCY: They have joints so they can move many ways. MOTHER: You may all put your arms out straight. Now raise them above your head and then touch your head without bending them. HELEN: We can’t do it, mother. MOTHER: Let us see, then, how many joints, or bending-places, we have. We will call them the hinges of our house, for they help us to use our limbs, just as the hinges of a door help us to open or close the door. Please bend your arm and tell me how many parts it has. PERCY: My arm has two parts. MOTHER: What do you think would be a good name for the part near your shoulder? AMY: The top arm, or upper arm. MOTHER: I think upper arm is best. Now if that part is the _upper_ arm, what would you call the other part? ELMER: The lower arm. MOTHER: It is also called the forearm. Now move your elbow joint backward and forward, and tell me what kind of joint it is. HELEN: It is like a door hinge, for I can move it only two ways. MOTHER: Yes, the elbow joint unites the upper and lower arm, and it can swing only one way. What shall we call the joint that joins the upper arm to the shoulder? [Illustration: The shoulder joint] PERCY: The shoulder joint. MOTHER: Is this joint like the one in your elbow?