CHAPTER II.
MUSCLES.
HAT makes the limbs move?
You have to take hold of the door to move it back and forth; but you need not take hold of your arm to move that.
What makes it move?
Sometimes a door or gate is made to shut itself, if you leave it open.
This can be done by means of a wide rubber strap, one end of which is fastened to the frame of the door near the hinge, and the other end to the door, out near its edge.