I hope I have told you enough, my dear child, to enable you fully to
estimate the force with which air presses upon everything on the surface
of the earth, and consequently upon our own bodies among the rest.
If you understand this, nothing is easier than to understand how air
comes and goes in our lungs.
When the cook wants to light her fire with two or three hot coals,
what does she do?
She takes the bellows and blows it, does she not?
But if she has no bellows at hand, what does she do? You answer at
once, she blows it herself with all the strength of her lungs.
By which it would seem--does it not?--that we are a sort of living
bellows, being able, in case of necessity, to act as a substitute for
the wood and leather ones of common use. And if we really possess the
power of doing the work of a bellows, may not this be because we have
within us some little machine of the nature of a bellows?
Exactly; and this fact gives me the opportunity of making you understand
the action of the lungs by explaining that of the bellows, which is
in everybody's hands, but which three-fourths of the people use, without
troubling themselves to inquire how it is made or acts.
"A bellows, as you know, is composed of two pieces of board, capable
of being separated and brought together again at will, and united by
a piece of leather so shaped and arranged that it doubles up when the
boards close, the intermediate space forming a firmly-closed box, the
size of which increases or diminishes at every movement of the boards.
"We take the bellows down to use it, and there are the boards, lying
flat upon each other, the box between them quite small. Is there
anything inside, do you think?
"Nothing," you answer; "the bellows is empty."
Do you think so really, my child? Do you think a tumbler is empty,
then, when you have drunk out its contents; and that jelly pots are
empty when all the jelly is eaten? There are not so many empty things
in the world, I assure you, as you suppose. You forget the air--that
monster who is always wanting to stretch himself out, and pushes against
everything he meets. He is an unceremonious gentleman, who takes
possession of every vacant place; as fast as you put a spoonful on
your plate, he takes up the room of the jelly which has been removed,
and at each mouthful you swallow, he slips into the place of the water
which goes away. When you think the glass and pot are empty, they are,
in reality, full of air. You cannot see it; but it is there, you may
rely upon it.
There is air, then, in the bellows-box, because there is air in every
place where there is nothing else to dispute possession with it. The
quantity is small in this case, no doubt, because the box is small and
cannot hold much.
But now, look! I separate the boards, and the box, which was small,
becomes large. For once, then, here is a box which must be partially
empty; for it has just, as if by magic, made a space in itself in which
positively there cannot be anything, since there was nothing there
beforehand.
Ay! but look down at the centre of the upper board. You see a little
hole there, do you not, and below the little hole a small piece of
leather, which seems to close it up? That is a _valve_, one of those
doors, such as we noticed before in the heart, and such as are to be
found, moreover, in most houses, which let people through on one side
but not on the other. This one opens when it is pushed from without, but
lets nothing out which has once got in. Now, the air outside, as I said
before, is always pushing against everything. He pushes as a matter of
course, therefore, against the valve, and as there is nothing behind it
to resist the pressure, in proportion as room is made inside the box, he
enters and fills it with himself.
But presently some one begins to close the bellows, and he finds himself
caught between the boards; on which these invite him to begone, with
the same sort of politeness displayed by the police, when the hour of
departure comes in a place of public exhibition; when, _i.e._,
they spread out on all sides, and force the crowd before them till
they have found the road to the door. But the air cannot get back by
the way it came in, the door being shut. As, however, it must go out
somewhere, whether it likes it or not, it passes through the tube at
the end of the box (the _nozzle_ of the bellows), and comes out
thence with a rush upon the fire. When it is once gone the bellows can
be distended again, and the process be repeated as before indefinitely.
And this is just what goes on inside ourselves. Your chest, my child,
is a box which expands and contracts alternately; making a place for
the air by the first effort, and then driving it out by the second.
It is neither more nor less than a bellows, but of a simpler
construction than that used by the cook. The exit pipe serves also for
a door of entrance, and there is but one board instead of two.
The _exit pipe_ is the _larynx_, of which we spoke before,
when we were talking of swallowing the wrong way, and which communicates
with the air outside, through the nose and mouth at the same time,
allowing us to breathe through either one or the other as we like.
As to the _board_, I said a few words about it when I was describing the
liver. It is the _diaphragm_--that separating partition--that floor
which is placed between the two stories or divisions of the body--the
belly and the chest.
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.
In its natural position it bulges upwards in the middle, like a cloth
swollen out by the wind, and thus occupies a portion of the chest at
the expense of the lungs. When air has to be admitted, its _fibres_
tighten and bring it flat again, as you and your brother brought the
handkerchief flat just now by tightening it.
The whole space previously occupied by the arch of the _diaphragm_
is thus given up to the lungs, which, being elastic, instantly stretch
themselves out to it; while air, running in through the nose and mouth,
fills up in proportion the empty place (_vacuum_) created by the
extension of the lungs, exactly as in the case of the bellows.
But soon the fibres of the _diaphragm_ relax. It rises up again into its
old position, driving back the lungs as it does so; and the air finding
there is now no room for it, goes out by the same way the other came in.
I say _the other_, observe, because the air that goes out is no longer
the same as when it came in; and this is the secret of _why we breathe_;
while the up and down movement of the _diaphragm_ is the explanation of
_how we breathe_.
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 nobody'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 passes 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? God,
your catechism tells you. The same God made both; did he not? We do
not acknowledge two. And if it be the self-same God 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 God. The whole human race, taken
in the mass, 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
constituted 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 God has passed 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_ constituting 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 circumstances, 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 canal, which passes 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 partitions 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.