MOTHER: That is right. The one at the hip, as I have said, is a ball-and-socket joint; the one at the knee is a hinge joint, and the ankle is quite like the wrist. Then we have the foot, with a number of small joints, like the hand. PERCY: But we have toes on our feet instead of fingers; still there is the same number. MOTHER: Yes, and some people can use their toes to draw pictures, write, and do many other things. Now we have found what our body-house is like on the outside, and we see how well each part is made for the work given it to do. SUBSTANCES IN THE BODY MOTHER: Percy, do you remember what men use in building houses? PERCY: They use stone, wood, brick, iron, glass, lime, and paper. HELEN: And some houses are made of earth and straw. MOTHER: Yes, and some of these things are found in the body-house. AMY: Why, mother, we are not made of wood, stone, glass, or lime! MOTHER: That is true; yet some of these very things are in your body. Those who have studied the blood tell us it is iron, partly, that gives it its rich red color. You saw what a pretty red it is when you cut your finger to-day, Helen. Some of the things of which glass is made are in our hair and finger-nails, and our bones would soon become useless if we did not give them plenty of lime. PERCY: But how do the iron and lime get inside of us? That is what I would like to know. MOTHER: It does seem strange, but the houses we live in are made of what we eat. I once knew a young lady who thought she needed more iron in her blood, so she put some nails in water and let them stay till it was full of iron rust, and then she drank it. Perhaps if she had thought her bones needed lime, she would have taken lime water; but this is not the proper way to get iron and lime “inside of us,” as Percy says. We can not eat iron and lime, but grains and fruits can, and we eat the grains and fruits. Iron is found in apples, tomatoes, and strawberries. We get lime in wheat, peas, beans, and other foods. Have you noticed how the men are building that brick house across the street? AMY: They put one brick on top of another, till thousands of them are used in making one house. [Illustration: Bricklayer at work] MOTHER: Well, that is the way the house we live in is built, only instead of bricks it is made up of what are called “cells.” These cells are little bags filled with something that looks like jelly. They are so very small we can not see them at all unless we look through a glass which makes them seem much larger than they really are. Some of these powerful glasses make a speck of dust look as big as a large rock. ELMER: I wish we could see some cells.