But here especially the infinite superiority of the works of God over the miserable inventions of man comes out in all its grandeur.
A bellows which was to have the honor of keeping up within us that miraculous fire—the pre-eminently sacred fire—which we call Life, required something more than a common board for its foundation. And accordingly this, of which I am now going to give you a detailed history, is as marvellous as it is admirable. I fancy that when you have read my account, you will no longer turn up your nose at the vile word diaphragm.
Let us first take a peep at the construction of the bellows.
On each side of the vertebral column, from the neck to the loins, spring twelve long bones, one below the other, bent in the form of bows; these are called the ribs. The first seven pairs of ribs rest, and as it were, unite, in front, upon a bone called the sternum, which you can trace with your finger down to the pit of the stomach, at which point the finger sinks in, for there is no more sternum, and the last five ribs on each side no longer unite with those of the opposite one. For which reason they are called false ribs. On the other hand they are joined to each other at the ends by means of a strip or band of a substance sufficiently strong, but at the same time flexible, and somewhat elastic, which is called cartilage or gristle. The next time you see a roasting piece of veal on the table, look well at it, and you will see at the end a white substance which crackles under your teeth; that is gristle.
This forms the framework of our bellows, which you may picture to yourself as a kind of cage, widening towards the bottom and going to a point at the top, for the arches formed by the upper ribs are smaller than the others. The whole terminates in a sort of ring, through which pass, together, the oesophagus and the trachea.
The space between the ribs is occupied by muscles which reach from one to the other, and the whole framework or cage is shut in below by the diaphragm, that marvellous board whose history I have promised to relate.
The diaphragm, as I told you some time ago, is a large muscle, thin and flat, stretched like a cloth between the chest and the abdomen. It is fastened by an infinity of little threads called fibres, to the lower edge of the cage I have just been describing, and it looks at first sight as if it must be incapable of moving, since it is fixed in one invariable manner all round the body.
It moves nevertheless, but not in the same way as the boards of our bellows.
Ask your brother to hold two corners of your pocket-handkerchief; take hold of the other two yourself, and turn the handkerchief so as to face the wind. The four corners remain in their place, do they not? but the middle, inflated by the wind, curves and swells out in front like a ship's sail, which itself is only an immense hand kerchief after all. Then draw the handkerchief tightly towards you, each to your own side, and it will recover itself and become flat again. Loosen it a little and it will curve and swell out again in the middle, and this maneuver you can go through as often as you choose.
Which very maneuver the diaphragm is continually performing, of and by itself.