As you perceive, then, the mechanism of these bellows of ours, is of the most simple, and consequently of the most ingenious character, and leaves far behind it anything we have ever imagined.

Are you disappointed? Do you feel inclined to exclaim, "Is this all?"

to ask where are the wonders I promised you? to protest that I may talk as I please about the inflating and flattening of a pocket-handkerchief? _you_ can see nothing so marvellous in the matter; nothing worth making your mouth water for.

A little patience, Mademoiselle! Hitherto we have talked only of the machine; but there is a goblin inside it, and our fairy tale is going to begin again.

There are in some families certain old servants who belong to the house, more, it may be said, than their masters, in some ways. They educate the children, and they serve them till death; they live for them alone, and know so well what they have to do, both by day and night, that there is no need to give them any orders. Nay, not only is it unnecessary to give them directions--it is for the most part labor in vain. They are so completely at home in their business, that they will go n.o.body's way but their own. If you wish them to alter their habits they may obey you for an instant, but it is only to return into the old groove directly after; for they know better than you do what you want.

I was very little when I first read in the story-books of my day, some bitter complaints of the disappearance of this race of old-fashioned servants of the good old times. And you very likely may have seen it said that they are no longer to be met with. Yet there will always be some, depend upon it, in families, who know how to make and to keep them. Good old times or not, they have never been found in any other but these cases.

Still, _I_ have just such a one as I have described--even I who am talking to you--and so has your mamma; and what is more, you have one yourself; and what is more still, everybody else has one. This servant of the good old times, who will never disappear (and this is more than one can promise of any other) is the _Diaphragm!_ When you came into the world, my dear child, and were merely a poor little lump of flesh, without strength, intelligence, or will; incapable of giving any orders whatever to those organs of yours, of whose existence you were not even aware, your _diaphragm_ quietly began his duties, without leave or inquiry from you, and with your first _breath_ your life began. Since which he has always gone on, whether you attended to him or not, and his last effort will be your last sigh.

When you go to sleep, careless of all that is to happen, until you awake again, that servant of yours, indefatigable at his post, labors for you still, and the light breath which half opens your rosy little lips as it pa.s.ses through them; that light breath which your happy mother watches with such pleasure, is his work. Midnight strikes--one o'clock--two; all around you are buried in sleep--but he is awake still. Were it otherwise--were he to go to sleep when you do, you would never awake again!

This protector of each instant, this faithful guardian of your life, is, nevertheless, subject to you as a servant to his master. Attend to him, and he will obey your orders. You can make him go at a great pace, or slowly, as you choose; or stop him altogether, if the fancy takes you to do so: but this not for long. The servant of the good old times is obstinate in the performance of his duties. He will yield to you in trifles; but do not try to force him over serious matters. I have read somewhere of a desperate young fellow, chained down in a dungeon, who killed himself by holding his breath; but I never quite believed it. Mr. Diaphragm would not allow any one to carry rebellion so far as that.

But we have not finished yet, and you do not yet know how appropriate is the comparison I am making.

Should any misfortune, any grief, any trifling annoyance even, befall his master, a good servant suffers with him, and as much as he does; sometimes even more. Occasionally the master is comforted, while he remains still disturbed.

"And the diaphragm?" you ask.

The diaphragm does precisely the same, my dear child. Yours, especially, shares in all your griefs to such an extent that, truth to say, he is not always quite reasonable. The other day when your mamma did not want to take you into the country with her, he was so sorry for you that he went into perfect convulsions, and you sobbed and sobbed till she was obliged to say, "Come, then, you naughty child;" whereupon you embraced your mamma, and were quite happy again, while he remained still unappeased, and your poor little chest was shaken more than once afterwards by his last convulsions.

Sobbing, you must know, is merely a convulsion--a great shake of the diaphragm--which is the reason of its causing such a heaving of the chest.

It is the same with respect to joy. The joy of the master makes the servant dance, and so the diaphragm too! Its little internal jumps are, then, what we call laughter--a thing you are well acquainted with.

Put your hand on your chest next time you laugh (and I hope it will be soon) and you will feel how it dances--thanks to the diaphragm which jumps for joy whenever it finds you in good humor.

Please to observe further, that nothing of all this is done to order.

He starts of himself, poor fellow, without waiting to ask if you will ever know anything about it; and, in truth, you have known nothing about it up to the present moment.

What say you to the diaphragm now, my child? Does not the very name please you? You scarcely expected to find there--under your lungs--so good a servant, one so attached to your person, so strongly resembling in all points the best specimens we know among men. And still we have not done. I have reserved as a finale for you a new point of resemblance which will make you open your eyes very wide indeed.

The old servant is sometimes cross and grumbling. If anything is going against his grain in the house he has no scruple in saying so; and his mode of speaking is sometimes rather rude. Nor is it of any use to get impatient and impose silence on him; he will listen to nothing--it is his privilege. But let some unforeseen accident happen to his master, let him see him deeply affected, and in a moment all his anger is over.

He sets himself silently to work again, recalled to order twenty times sooner by his master's emotion than by his utmost impatience.

You ask what I am coming to now? My dear child, what I have just told you is the history of the _hiccup_--the history of the hiccup, neither more nor less.

I must first tell you, however, that the _diaphragm_ keeps up intimate relations with his neighbor below--the stomach. Every time he rises in the breast the stomach rises behind him; and not only the stomach, but also its companions, the intestines. All the officials employed in the business of digestion travel regularly with him; coming down as well as going up in company. Put your hand upon your abdomen and breathe strongly and you will feel the rebound of all the movements of the diaphragm.

Now, when matters are going on wrongly inside, when too much work has been imposed on the officials, or work they dislike, or else when they have been disturbed in their labors, it will sometimes happen that the _diaphragm_ takes part with his comrades in the abdomen. He gets angry then, and shakes his master, who cannot help himself a bit. You must be very well acquainted with these attacks, which are very fatiguing when they last long. One begs pardon and resists him in vain; he does as he pleases, without stopping to listen, turning everything upside down; and do you know the only efficacious plan for calming him at once? It was a constant source of wonder to me when I was little.

A sudden fright, a start unexpectedly caused by a friendly hand slipping secretly behind, and laying hold of one, was all-sufficient; disarmed by the agitation you have undergone, the naughty, stubborn muscle forgives you, and you are cured.

Having dwelt so long on the truly wonderful resemblance between the proceedings of two sorts of beings, whom no one that I know of ever thought of comparing together before, I will now, my dear child, give you the key to all these comparisons, which seem so whimsical at first, but are so striking in reality, and which come to my pen of their own accord, as it were, in the midst of the explanations I have undertaken to give you. Many people who would not themselves care for them, will declare that they are too hard for a little girl to follow. But for my own part, I find that the eye can take in a mountain as easily as a fly, and that it is not more difficult to lay hold of great ideas than of little ones. It is short-sighted people, not children, who cannot see far before them. Who made the heavens and the earth? G.o.d, your catechism tells you. The same G.o.d made both; did he not? We do not acknowledge two. And if it be the self-same G.o.d who made everything, the hand of the universal Maker will be found everywhere; and from the highest to the lowest portion of His work the same mind will manifest itself under a thousand different forms. Not only, either, is each man separately, one by one, the work of G.o.d. The whole human race, taken in the ma.s.s, is also His creation; and the laws by which human society--that great body of the human race--seeks to regulate itself for the preservation of its existence, are undoubtedly the same as those which overruled the organization of our individual bodies. It is not very astonishing, then, if we find, in the life of human society around us, details corresponding with each detail of the life of the human body, or, at any rate, closely resembling them. What would really be astonishing, would be that mankind as a whole should be differently const.i.tuted from man as an individual, and that human society should have other appointed conditions of well-being than those of each of its members.

So, while I am on the subject, I should like to advise those who wishto apply themselves to what is called _politics_--that is to say, social life--to begin their studies of the body social, by studying the body human, first. They will learn more from it than from the newspapers!

But you have nothing to do with all this. For the present, take notice of one thing only; viz., that the hand of the same G.o.d has pa.s.sed over everything, and that there is neither much presumption nor much merit in tracing points of comparison between the different parts of His work. These comparisons are not a mere play of the mind; they really exist ready made in the very foundations of things.

Now let us come down a little from these heights and return to our friends the lungs. I have not spoken about them for some time, and I have not yet told you how they are constructed.

I wish I could show you some, but the cook will do so, if you would like to see them. The _lights_ with which she feeds the cat and the dog are the lungs of some animal.

Take up a piece in your hand, and you will find you have got hold of something _light_ (cooks have not given it its name without a reason), which is also soft, sinks under your finger if you press it, and rises again afterwards like a sponge. In fact, the lung, like the sponge, is composed of an infinity of minute cells, whose elastic sides can be contracted or expanded at will. They are like so many little chambers, into every one of which blood and air keep running hastily, each on its own side, to bid good day to each other, touch hands, and then hurry out as briskly as they came in. Whether the bit of lights the cat is eating, comes from an ox, a pig, or a sheep, you may look at it with perfect confidence; your own lung is precisely like it. You would see nothing different, could you look into your own chest.

So much for the _substance_ of the lungs. As to SHAPE, imagine two large, elongated packets, flat inside, descending right and left, inside the breast, and bearing the heart, suspended between the two, in the middle. The extremity of each packet descends below the heart, and it is in the interval which separates them that the arch of the diaphragm performs its up and down movement.

I have already said that air reaches the lungs through the _larynx_. The _larynx_ (of which we shall speak further when I have explained another curious thing very valuable to little girls--the voice), the _larynx_ is a tube composed of five pieces of _cartilage_ (you know now what _cartilage_ or _gristle_ is), the firm resisting texture of which keeps it always open. After these five pieces of _cartilage_, come others, and the tube is continued; but it then takes the name of the _trachea_; the _larynx_ and _trachea_ const.i.tuting the _windpipe_. At its entrance into the chest, the _trachea_ divides into two branches, which are called _bronchial tubes_, and which run, one into the right lung, the other into the left. You sometimes hear people talking about _bronchitis_. It is an inflammation of these _bronchial tubes_, which are within an inch or two of the lungs. It is necessary, therefore, to be very careful in such circ.u.mstances, and do exactly what the doctor prescribes, because--one step further, and the inflammation extends from the bronchial tubes into the lungs themselves, with which it is not safe to play tricks.

Having reached the lungs, the _bronchial tubes_ subdivide into branches, which ramify again in their turn like the boughs of a tree, and the whole ramification terminates in imperceptible little tubes, each of which comes out in one of those little chambers I was talking about just now. And this is the way in which air gets there at all.

The venous blood which leaves the heart, arrives on its side by one large ca.n.a.l, which pa.s.ses out from the right ventricle, and which is called the _pulmonary artery_. And, to tell you the truth, while there is no learned man present to be angry with us, it is a very ill-chosen name, because it is _venous_ blood which flows in this so-called _artery_. But the doctors have decided that all the vessels which run from the heart should be called _arteries_, and all those which go back to it _veins_, whatever may be the nature of the blood which they contain. We cannot help it, because they manage all these matters in their own way; but in that case it was scarcely worth their while to talk about _arterial_ and _venous_ blood. It would have been better to have said simply, red blood and black blood.

Be this as it may, _venous blood_ arrives from the right _ventricle_ through the _pulmonary artery_. This divides itself, like the _bronchial tubes_, into thousands of little pipes, whose extremities come creeping along the part.i.tions of the little chambers in question.

And here, then, takes place, between the air and the blood, that mysterious intercourse for the account of which I have kept you waiting so long; and at the end of which the black blood becomes red, or, in other words, from venous becomes arterial. I have called it "intercourse," and this is really the proper phrase; for this transformation of the blood is accomplished by means of an exchange.

The air gives something to the blood, and the blood gives something to the air--each giving, in exchange, like two people over a bargain in the marketplace.

With your permission, my dear child, we will stop here to-day. We have now got to the charcoal market, and it is a little black.

LETTER XX.

CARBON AND OXYGEN.

Here, then, my dear child, we have arrived at the explanation of that great mystery, WHY _we breathe._ Keep on the alert, for we are now entering into a region where everything will be new to you.

Here we are at the charcoal market, I said to you just now, and no doubt you concluded that I was beginning another comparison.

But no such thing; there is no question of comparison or simile here; I state the fact itself, pure and simple as it stands: it is a _market,_ for commercial intercourse and exchange are carried on there, as I told you before, and it is a _charcoal_ market, because _charcoal_ is, positively, the essential and chief article of commerce.

You are astonished, I dare say, and are ready to ask me whether I can possibly mean real charcoal, charcoal such as the cook puts into the furnace. Surely, say you, we have nothing like _that_ in our bodies?

Surely we don't eat _that_?

But I answer yes; real, true charcoal, and you do not dislike it; you eat of it even daily; nay, you do not swallow a single mouthful of food which does not contain its proportion of charcoal.

You laugh; but wait a little and listen.

When you are toasting a slice of bread for breakfast, and hold it too near the fire, what happens to it?

It turns quite black, does it not?

When mutton-chops are left too long unturned on the gridiron, what happens to them?

They turn quite black also.