Bones of the chest.
Look at this barrel-shaped set of bones that make the chest. The ribs go round it as hoops do round a barrel. They are joined to the back bone behind and to the breast bone in front. They are joined to the back bone in such a way that they move up and down as you breathe. You can feel them move upward if you put your hand on your chest as you take a full breath. Inside of this barrel-shaped set of bones are the heart and lungs.
Back bone.
Bowing.
The back bone, as we call it, is not one bone; it is a chain or pile of twenty-four bones placed one above another. You can see a part of this pile or column, as it is sometimes called, in the figure of the bones of the chest. If it were all one bone, you could not twist your body about as you do. And in making a bow, you could not bend your back. You could only bend your head forward on the top of the back bone, and bend your body forward on your lower limbs. A very awkward bow that would be. As it is, whenever you make a bow, there is a little motion between each two of the whole twenty-four bones, and this makes the bow easy and graceful. Persons that bow stiffly do not have enough of this movement in the column of bones, but move it altogether, very much as if it were all one bone.
Position of the head.
The head rests on the top of this column of bones. When you move your head backward and forward, it rocks on the topmost bone of this column. There are two little smooth places hollowed out on this bone for it to rock on, and the head has two smooth rockers that fit into these places.
Questions.—In what two ways does the mind use what it learns? With what does it do this? What are the inlets of the mind’s knowledge? What are its outlets? What move the bones on each other? What is said about the wearing of the joints? What is said about their being kept oiled? What are the bones to the body? What is said about the bones of the head? What of the bones of the chest? To what are the ribs fastened behind? To what in front? How many bones are there in what is called the back bone? Why are there so many? What does the head rest on? What is said about the motion of the head?