But the science that teaches us all that is known about our bodies is a very difficult study, and there are many hard names to master, even at the very outset. For instance, when we speak of the bony framework—that skeleton which, as you know, belongs to us in common with the vertebrate animals—there is a great deal which you would find very difficult to remember.
Still, as I daresay you have found out, the more we learn, even of difficult sciences, the more we can learn, and little May (though, to be sure, she is now four years older than she was when you first made her acquaintance) has learnt a good many of the hard words. She could show you upon her own round arm, just where the bone which reaches from the shoulder to the elbow begins and ends, and tell you its name, and the names of the two bones which reach from the elbow to the wrist, and of the wrist-bones, and of those which you can feel in the palm of your hand, and the finger-bones.
But when you hear that you have more than two hundred bones in your body, you will be inclined to agree with me that it would take both of us some time to learn even their names, much more to know all about them.
The spine consists of twenty-four short bones, each with a little ring. These vertebras are piled up one upon the other; for God has made our bodies upright; our faces, are lifted upwards, and our eyes look straight before us. These twenty-four little bones are closely and strongly bound together, and between each one and its neighbour there is something so soft and elastic that we can bend our heads, or move in any direction, without the slightest strain or jar.
The head is most wonderfully built up, like an arch, of several bones beautifully joined in a very strong and perfect way which carpenters call "dove-tailing." We can understand why the head, which is so much exposed, and is almost entirely occupied by the brain, should be so carefully protected; for thought, memory, will, and what we can best express as "consciousness of our being," all depend upon it.
Passing from head to foot, we find that our feet, which are not large, yet must bear the weight of the body, are also made upon the arch-principle, which has been found, like the hollow bones of the bird's wing, to combine lightness and strength. The twenty-six bones are so fitted together that this wonderful arch is quite elastic, as you can prove by moving your own foot up and down.
The joints, where two bones which are to play upon each other come in contact, as they do at the elbow or shoulder, are made in different ways. The elbow only moves to and fro like a hinge; the hip and shoulder, like a "ball and socket," move every way. You do not need to be told that each kind of joint is found just where it is needed for the work it has to do; for there is no mistaking or misplacing in God's workmanship, as there so often is in the very best of ours.
I cannot at present tell you anything about the muscles, except that it is by their means that we move arms, legs, head, eyes—every part of the body, for bones cannot move of themselves, but are acted on by the muscles.
Nor can we learn much about the nerves, because the subject is very difficult to understand. They come from the brain in the head, and from that part of it which runs all down the backbone, through the little bony rings of the vertebræ; and they are protected, because they are so very delicate, and so precious to us, by a strong bony sheath. At first these nerves are like coarse twine, but they divide and divide until they become as fine as threads of white silk—almost as fine as the stronger part of a spider's web—and they go all over the body, reaching to the very tips of the fingers.
The first pair of nerves goes to the nose, for smell; the second to the eye, for sight; and so on for hearing and taste. These are the nerves called "sensory," which carry to the brain sensations from outside the body. The "motor" nerves are those which take orders from the brain, to be instantly obeyed by the muscles.