The History of a Mouthful of Bread
by
Jean Mace
Part 2 out of 6
while at dinner, give him more work to do than he is capable of doing.
Although he is the master, he is but a puny fellow, as I have already
pointed out; nevertheless, he works conscientiously, because he knows
that the life of the whole body depends upon his exertions. Some people
even say that in spite of his leanness he strips himself, at each
digestion, of his interior skin, which he sacrifices to his work, and
the fragments of which tend to increase and improve the stew which is
entrusted to his care. Think of this, my dear, whenever a greedy fit
comes over you, and recollect that such a disinterested public
functionary deserves some consideration. Besides, there is serious
danger, quite apart from any question of injustice, in overwhelming
him with work. If your legs are wearied out, you have it in your power
to lie in bed. If your arm is in pain, you can keep it at rest. But
your stomach is like those poor people who have to support their
families by the labor of each day. He, too, labors for others: he has
no right to rest, no right to be ill, therefore; and when he begins
to fail, woe betide you--you will have enough of it.
Children who have learnt nothing may laugh at all this, but you, my
dear, are beginning to know something, and "science constrains,"
_i.e._ it has its claims and requirements. It requires you, to-day, not
to be greedy, to-morrow, something else, and so on, continually, until
you have become quite reasonable and wise. I am sorry for you if this
vexes you, but it was your own wish to learn, and _science constrains_.
Indeed, I will whisper to you in confidence that this is the best excuse
people who are unwilling to learn have to offer for refusing. They do
not know what learning may lead to, and what a pity it would be if they
could no longer be greedy, or ill-natured, or selfish. What would become
of us all in such a case?
LETTER IX.
THE STOMACH--_(continued)_.
We made a very long story of the stomach last time, my dear child;
and, after all, I see that there was one thing I forgot to tell
you--viz., what it is like.
Have you ever seen a bagpiper, I wonder? A man who carries under his
arm a kind of large dark brown bag, which he fills with air by blowing
into it, and out of which he presently forces the same air into a
musical pipe by pressing it gently with his elbow. If you never saw
such a thing, it is a pity; first, because the bagpipe was the national
instrument of our ancestors the Gauls, and is religiously preserved
as such by the Scotch Highlanders and the peasants of Brittany--(two
remnants of that illustrious race, whose history I recommend to your
careful perusal some day); secondly, and it is this fact which has the
greatest interest for us just now, because that large bag, which is
the principal part of the instrument, gives you a very exact idea of
your stomach; for in fact it really and truly _is_ a stomach itself, and
moreover, the stomach of an animal whose interior formation resembles
yours very, very much.
And who do you suppose is this audacious animal, which presumes to
have an inside so like that of a pretty little girl? Really, I am half
ashamed to name him, for fear you should be angry with me for doing
so. It is--it is the pig! The resemblance is not exactly a flattering
one to you, perhaps, but we are all alike, and it would be worse than
foolish to grumble at being created as we are. Moreover, there is one
difference; the pig, who thinks of nothing but eating, has a very much
larger stomach than we have, which is some consolation, at any rate.
Place the palm of your right hand on what is called the pit of the
stomach, turning the ends of the fingers towards the heart; your hand
will nearly cover the space usually occupied by the stomach, and you
may figure it to yourself as a rounded and elongated bag, bigger above
than below, making a very decided bend inside as it descends from the
heart downward; something like one of those long French pears, called
"Bon-chretiens," if it were bent in the middle, and the big end of it
were placed next the heart. As for the exact size of the bag, there
is no telling it, for it depends upon circumstances. It is a very
convenient bag in that respect; just such a one as you would like to
have in your frock for a pocket; only there would be a danger of your
being tempted to put too many things into it. For as you fill it, it
expands, and enlarges itself like an indian-rubber ball, which, though
only the size of an egg to begin with, becomes as big as your head if
you blow hard into it. Then, as it gets empty, it recovers itself,
diminishing gradually in size in plait-like contractions.
When people remain too long without eating, they have, as they say,
twinges in the stomach. This is because the stomach, becoming by degrees
quite empty, and contracting more and more, the surrounding parts which
were sustained by it, lose their support, and strain at their ligaments,
which now have all the weight to bear. Careless people, who do not
think of such things, are reminded by the twinging pains that it is
time to eat, just as a careless servant is called to order by the bell
of which his master has pulled the string.
In your case, my dear child, such warnings are soon attended to, and
you have not always even to wait till they come. But there are hundreds
of miserable beings who are warned to no purpose, who cannot obey the
master when he calls for his rations, because they have nothing to
give him; and when this forced disobedience lasts too long, they end
by dying of it. In cases like these, when human beings thus cruelly
perish, the stomach is found to be contracted till it is scarcely
bigger than one's finger.
On the other hand, a man once died suffocated from excess of food,
after one of those great public dinners, which last four, six, or more
hours--one can scarcely say correctly how long--and the doctors who
examined him found his stomach so prodigiously enlarged that it alone
occupied more than one-half of his inside. As you perceive, therefore,
the stomach has, properly speaking, no fixed size. Its size depends
upon what there is in it. It is like those men whose manners go up and
down with their fortunes; who seem very grand people when their pockets
are well filled, but become very small ones when their purses are
empty. There is, nevertheless, this difference between them, that such
men are fools, because they are men, and not _bags_; whereas the
stomach is a sensible bag, fulfilling with intelligence the duties of
its character as a bag. It is very fortunate for us that it is ready
to change its size, according to the caprices of our appetite; and
dressmakers would do well if they could get a hint from it how to
improve their style of pockets, which certainly cannot have cost their
inventors any very great effort of imagination!
The way in which this extraordinary pocket empties itself is not less
curious than the rest. As long as digestion is going on, the stomach
is firmly closed at each end; at the upper one by the last ring of the
_aesophagus_, and at the lower by another ring of the same kind,
only stronger; the watchful guardian of the passage which leads to the
intestines. This ring is called the _pylorus_.
For once, here is a name which agrees with our method of describing
the human machine, and I have much pleasure in translating it to you,
although it is a Greek word. _Pylorus_ is the Greek for a porter;
and our ring is indeed a porter like the one of which we have already
said so much, and which I called last time the _porter up above_,
in anticipation of his colleague below.
The porter up above presides at the entrance; the one below at the
exit, and both for the same purpose, namely, to _taste._ [Footnote:
It would be absurd to say so in the common acceptation of the term;
but according to No. 1 of Mr. Mayo's "Classification of the impressions
produced by substances taken into the fauces," viz., _"Where
sensations of_ touch _alone are produced, as by rock-crystal,
sapphire, or ice,"_ the word taste may be applied to the
discriminating faculty of the _Pylorus_.--TR.]
It may well astonish you, that you should have in your inside a taster
who is not accountable to you; who experiences sensations of which you
know nothing, and cannot even form an idea. Yet thus it is. The
_pylorus_ actually tastes the paste which is in the stomach, and
if it is not to his taste, that is to say, if the work of digestion
has not sufficiently transformed it for use, he keeps the door
relentlessly closed.
The porter up above has a thousand different tastes. He makes his bow
to meringues, and admits wings of chickens. Fries, roasts, stews,
things tender or crisp, sweet and salt, oily, greasy, or sour; amongall
kinds he has friends whom he welcomes in succession; and it is
well for us that he does so, for we share in all his pleasures.
The porter below, who works for himself alone, obscure and unknown
down in his black hole, the porter below, I say, has but one taste,
knows but one friend--a gray-looking paste, semi-liquid, with a very
peculiar unsavoury smell, disagreeable enough to any one but himself,
which is called the _chyme_, I scarcely know why, but it is what
everything one eats turns into, without exception, be it delicate or
coarse by nature. The great lord's truffle-stuffed pullet makes, as
nearly as possible, the same _chyme_ as the charcoal-burner's black
bread; and though the palate of the former may be better treated
than that of the latter, the _pylori_ can enjoy but one and the
selfsame sauce. Equality is soon restored in this case, therefore, as
you see.
To be free to pass through then, the contents of the stomach must be
reduced to the condition of _chyme,_ the only substance which finds
favor with the _pylorus:_ and as, in the endless varieties of food which
go to form our nutriment, some sorts turn into _chyme_ much more quickly
than others, it follows, that by the aid of its discriminating tact
(which is not easy to elude) the _pylorus_ allows some to pass, while it
turns back others, until all in succession are converted into chyme. For
example, in the case of a mouthful of bread and meat swallowed at once,
the bread passes away on its travels long before the meat has done
dancing attendance in the stomach, awaiting that transformation without
which the _pylorus_ will never allow it to slip through.
This ought to make you seriously reflect on the danger of carelessly
swallowing things, which, by their nature, are not susceptible of being
converted into _chyme,_ particularly if they are too large to
hide in the general paste, as a cherry-stone will sometimes do, so
mixed up with other food as to pass unperceived by the _pylorus,_
over whose decisions we have no control, remember. It bangs the door
to, be assured, in the very face of anything obnoxious without
hesitation, and the poor stomach would find itself condemned to retain
them for an indefinite period, unless by dint of prayers and
supplications they should contrive to soften the stern guardian, who
may at last get accustomed to their approach, and, perhaps, in a weak
moment, allow them to pass as contraband goods; like a custom-house
officer on a foreign frontier who will occasionally shut his eyes to
a country friend's packet of tobacco. But the poor stomach has had to
suffer a martyrdom meantime, while the dispute was pending, and before
the intruder has been winked at by the porter.
I shall remember all my life the history of a peach-stone, which was
related to me in 1831. I was at the time a youngster at the Stanislaus
College, and (aided perhaps by the Revolution of July, which had
recently occurred), it was just then discovered to be a proper thing
to set about teaching the laws of nature to children. Consequently,
for the first time in the history of schools, a professor of natural
history was added to the instructors of Latin and Greek. I leave you
to judge how we opened our ears to his lessons. When we arrived in the
course of our new studies at the _pylorus,_ of which we had none
of us ever heard before, our professor, in warning us, as I have done
you, of the dangers of imprudent gluttony, related, as an instance,
the case of a lady who had inadvertently swallowed a peach-stone. For
two years she suffered agonies in her stomach without any cessation
or relief. The luckless peach-stone, repelled by the walls of the
stomach, which its very touch irritated, was incessantly thrown against
the entrance of the _pylorus,_ but in vain. As to turning itself
into _chyme,_ such a thing was not to be thought of, it was far
too hard a substance for that. Round and round it went, causing in its
relentless course such renewed suffering to the poor patient, that she
was visibly sinking from day to day.
The doctors, finding all their treatment of no avail, began to despair
of her life, when one fine day she was suddenly, and as if by
enchantment, relieved of her tormentor. The peach-stone had bribed the
porter, with whom, in the course of the two years, it had scraped up
a sort of friendship. It had cleared the terrible barrier, had been
allowed to slip out, and the lady was saved; but it was only just in
time.
I do not know, my dear, that this story, which is certainly well
calculated to cure you of any fancy for swallowing peach-stones,
willmake as much impression on you as it did on me five-and-twenty years
ago. The idea of telling it to you occurred to me quite by chance. It
has carried me back to the time when, as is now the case with you, the
mysteries which lie hidden in our internal organization were beginning
to be revealed to my mind; and you will one day know with what delight
one recalls the remembrance of these first dawnings of the intellectual
life--that delightful infancy of the growing mind--more rich in
recollections, and more interesting a thousand fold than the infancy
of the body. I have allowed myself the little treat of this episode,
and if I have had the good fortune to amuse you at all during our
progress, you must not cavil at this piece of self-indulgence.
And now we have done just what the peach-stone did; we, too, have
passed the barrier, and are out of the stomach, but still we have not
yet come to the end of our tale.
LETTER X.
THE INTESTINAL CANAL.
I venture to hope, my dear child, that more and more light is dawning
upon your mind, as we gradually proceed on our little journey. You
must by this time have some idea how the food, which has been masticated
and softened in the mouth, cooked, kneaded, and decomposed in the
stomach, and transformed into a soft, semi-transparent kind of paste,
will soon be ready to mix with the blood, in order to repair the waste
that the life-stream is continually undergoing in its ceaseless course
through all parts of the body.
You have perhaps thought it a sad degradation for a truffle-stuffed
fowl to turn to _chyme._ But when you consider that by this means
it becomes part and parcel of a human body, the change is not to be
despised. It was necessary, to begin with, that materials destined to
the honor of being incorporated into our frame, should break the links
which bound them to the condition of fowl and vegetable, and thus be
free to engage in new relations; just as a man who wishes to be
naturalized in a new country must first break the ties which hold him
to the old one. Those articles of food we were speaking of lately,
which are so stiff and ceremonious, and want so much coaxing before
they change into _chyme,_ which, moreover, we call _indigestible_
because they tire the stomach so much more than the rest, are merely
those whose component parts being held together by more solid ties than
usual, continue obstinately in the same state as at first, and will not
consent to that dissolution which is the first condition of their
glorious transformation.
Moreover, the transformation which has been described to you now, you
will henceforth meet with everywhere; wherever, that is to say, and
as far as, you choose to pursue the study of nature. God works by one
grand and simple rule so far as we can discover. He destroys to
reconstruct, builds up what is to be, out of the ruins of what has
been, creates life by death, if I may so express myself, and thus,
what takes place in our stomachs on a small scale goes on on a large
one in the universe.
Social communities, like everything else, are subject to this universal
law, and it is not always an advantage to them when they refuse to be
digested in the great stomach of the age!
While we are on this subject, and to show you how wonderfully this
little history of eating, told in this familiar style, applies right
and left, let us reflect on the causes which have produced a great and
mighty nation in one country (as in France), while in another (as in.
Germany), a far more numerous and even more intellectual population
has failed to rise to anything like the same distinction. The
explanation is not difficult. In the one case, the petty tribes among
which the land was originally divided consented to mix, and dissolve,
and be digested as it were together, in order to revive again for a
more glorious career; while in the other, the aboriginal societies
have adhered stiffly to their distinctive characters, and failing to
submit to the regenerating process, cling together in indigested
portions, rather than assimilate into one great whole.
However, we must return to the _pylorus_ or we shall be getting
into a difficulty! What I am now going to offer you though, is rather
hard of digestion, but it will not do to provide sweet pastry only for
your brain; it will be more wholesome for it to have something a little
more solid to bite at from time to time.
The _pylorus_, then, as has been shown, makes way for all sorts
of aliments when they have been converted into _chyme; i.e._,
when they have lost their original form and individuality. They are
dead to their first life, therefore; now the question is, how are they
to be revived into the new one?
Behind the _pylorus_ extends a long conduit or tube--so long as to be
sometimes seven times the length of the whole body, but doubled up
backwards and forwards a number of times, so as to form a large bundle,
which fills the whole cavity of the belly--or as we also call it, the
_abdomen_. This bundle or packet is known to everybody as _the
intestines_, and it is divided into two portions: the _small
intestine_--that is, the slenderer, finer portion which begins at the
_pylorus_, and forms all the doublings of the packet, and the _large
intestine_, which is shorter and thicker also, as its name implies, and
keeps to some extent separate, though it is in reality only a
continuation of the other. This starts at the base of the _abdomen_,
near the right side, goes up in a straight line to the height of the
stomach, below which it passes, making a large bend in front of the
small intestine; after which it descends on the left side to the lower
part of the trunk, where it terminates.
You will perhaps inquire how the _chyme_ continues to make its way
through all these manifold twists of the intestines; but do not trouble
yourself; it has only to let itself go. That _vermicular movement_ which
we noticed in the _oesophagus_ and in the _stomach_ is found here also.
It reigns, so to speak, from one end of our internal eating-machine to
the other; which eating-machine, by the way, we will now call by its
proper scientific name--_the intestinal canal_; and it is by that
movement the food is carried forward from the first moment it leaves the
mouth, and helped through all its journeyings, till it reaches the
termination of the large intestine.
If your body were made of glass, so that you could look through it to
watch the intestine at work, it would appear to you like an enormous
worm coiled up into a bundle, heaving and moving with all its rings
at once. You never suspected there was such a movement within you; yet
it has been going on there continually ever since you were born, and
will not cease till you die. Your internal machinery never goes to
sleep, not even when you are sleeping yourself. It is a workshop in
constant operation, providing night and day for your necessities; and
in this respect the inner man sets a first-rate example to the outer
one! You will recollect what I said to you the other day about the
internal republic, and the provinces which are under your sole
government. It would be very disgraceful for the kingdom to be doing
nothing while the republic is working so hard; and a queen who
understands her office will make it a point of honor to banish idleness
from her household; in the houses of her neighbors this word is unknown.
The _chyme_ once launched into this moving tube, is in no danger
of remaining stationary there; the fear is, of its passing on too
quickly, as you will soon see. But this danger has been provided
against. Along the whole course of its journey, though chiefly at the
commencement, it encounters at intervals certain elastic fleshy valves
which interrupt its progress, and do not allow it to pass till it has
accumulated in sufficient force to push them before it, and so escape.
In consequence of which it is always being checked in its advance; and
during these stoppages a most important work goes on upon it at leisure.
You must understand first, that the substances of which our food is
composed, and which are afterwards decomposed in the stomach, are not
all invited to enter the blood. Our aliments are something like the
stones which the gold-seekers of California reduce to powder in order
to extract therefrom the hidden particles of gold they contain. The
gold of our food is that portion of it which the blood is able to
appropriate to his own advantage; the rest he rejects as refuse. And
this explains why a small slice of meat nourishes you more than a whole
plateful of salad. Meat is a stone absolutely full of gold, while the
salad has only a few veins of it here and there, and by far the greater
part of the material it sends to the intestines, has, in consequence,
to be thrown away.
Now it is in the first portion of the small intestine, the part known
by the Latin name _duodenum,_ which signifies twelve (because it
is about the length of twelve finger-breadths), that the division takes
place between the parts which go to nourish the blood, and those which
are useless refuse. It is an important operation as you may suppose,
and were the _chyme_ to pass rapidly through the small intestine
the gold would run the risk of being carried off with the refuse.
After the delay in the stomach, the food-substances make another halt
in the _duodenum,_ which, being very thin and slender, would have
great difficulty in containing them at the time of their grand entry,
an hour or two after a meal, were it not that it possesses the property
of expanding itself to such an extent, that it swells out on grand
occasions to the usual size of the stomach itself, so that it has
sometimes been considered as a second stomach. And no doubt the
operation which takes place in it gives it a claim to the appellation,
for thereby the finishing stroke is put to the work previously begun
in the stomach, and one may fairly say that, but for this last touch,
very little would be accomplished at all.
Above the _duodenum_, and hid behind the stomach, is a kind of sponge,
similar in nature to those we have already observed in the mouth. To
this has been given the somewhat ridiculous name of _pancreas_; I call
it ridiculous because it is derived from two Greek words which signify
_all flesh_; whereas the _pancreas_, which is a sponge of the same
description as the salivary glands, presents the appearance of a grayish
granulous mass which is not fleshy at all. Whatever be its name,
however, our sponge communicates with the _duodenum_ through a small
tube, by means of which it pours into the _chyme_, as it accumulates, a
copious supply of a fluid exactly like the _saliva_ of the mouth.
Just by the place where the tube from the _pancreas_ empties itself into
the _duodenum_, another tube arrives bringing also a fluid, but of a
different sort. This last comes from the liver, where there is a
manufactory of _bile_--an unpleasant yellowish-green liquid, the name of
which you have no doubt heard before, and which plays a very important
part in the transformation of the aliments.
These new agents, the bile and the liver, are far too important to be
passed over in a few words; I reserve them, therefore, for my next
letter. Meantime, not to leave you longer in suspense, I may say that
the separation between the gold and the refuse in the _chyme_ takes
place as soon as the latter has received the two liquids furnished
by the liver and the _pancreas_. If you ask in what manner the
division is accomplished, I confess, to my shame, that I am not able
to explain it! What takes place there is a chemical process, and
hereafter I shall have occasion to explain the meaning of that phrase.
But the Great Chemist has not in this instance seen fit to divulge to
man the secret of the work.
Indeed, you must prepare yourself beforehand, my dear child, to meet
with many other mysteries besides this, if we pursue to the end our
study of this flesh and bone which constitute the body of man. And
here I recall what Camille Desmoulins is reported to have said about
St. Just, viz., that he carried his head as high as if it were a
consecrated Host.
[Footnote: The young Protestant reader who has never lived
in a Catholic country, will perhaps need to be told, that what
is here called Consecrated Host, is the sacramental wafer, or communion
bread of the church. In French called _hostie_, in Italian, _ostia_.
In all their religious processions, which are very frequent, the host
is carried by the priest highest in authority, in a glass box placed
on a staff about four feet long, which he holds before him and so far
elevated that he has to look up to it. Over his head a richly
embroidered canopy of satin is always carried by several men; and while
these are passing, all good Catholics uncover the head and bend the
knee, wherever they may be.
It is the custom also for the priest to be called to administer the
sacrament to any one about to die, on which occasion he always walks
under this canopy, dressed in his priestly robes, carrying the host
and preceded by some boys, ringing a bell, when the same ceremony is
observed. In passing a regiment or company of soldiers, the column is
halted, wheeled into line, and with arms presented, the whole line,
officers and men, kneel before it, and the priest usually turns and
offers a benediction. When he goes in the evening to the house of the
dying, it is customary for the people to go out upon the balconies
with lighted lamps and kneel while the host is being carried by.]
You will read about these two men by-and-by in history. Meantime I
will not bid you do exactly the same as St. Just, because you would be
laughed at; but in one point of view he was not altogether wrong. The
human body is, in very truth, a temple in which the Deity maybe said
to reside, not inactively, not veiling his presence, but living and
moving unceasingly, watching on our behalf over the mysterious
accomplishment of the everlasting laws which equally guide the
_chyme_ in its workings through our frames, and direct the sun
in its course through the heavens. We mortals eat, but it is God who
brings nourishment out of our food.
LETTER XI.
THE LIVER.
I fear you will be getting a little weary, my dear, of dwelling so long
on this intestinal tube, where things which looked so well on one's
plate become so transformed that they cannot be recognized, and where
there is nothing to talk about but _chyme_, and _bile_, and the
_pancreas,_ and all sorts of things neither pleasant to the eye nor
agreeable to the ear.
But what is to be done? It is always the same story with useful things.
The people by whose labor you live in this world, are by no means the
handsomest to look at, and so it is in the little world we carry about
in our bodies.
Never mind! Keep up your heart. We are getting to the end. We shall
very soon be following the nourishing portion of our food, on its
journey to the blood, and you will find yourself in new scenes.
First, though, let us say a few words about the liver--the
bile-manufacturer; and to begin with, I will describe the place he
occupies in our interior.
The interior of the human body is divided into two large compartments,
placed one above the other; the _chest_ and the _abdomen_. These are two
distinct apartments, each containing its own particular class of
tenants: the upper one being occupied by the heart and the lungs (the
respective offices of which I will presently explain to you); while in
the lower are the stomach, the intestines, and all the other machinery
which assists in the process of digestion. These two stories of
apartments are separated as those of our houses are, by a floor placed
just above the pit of the stomach. This floor is a large thin, flat
muscle, stretched like canvas, right across the body; and it is called
the _diaphragm_--another hard word! Never mind; but do your best to
recollect it, for we shall have great need of it when we come to the
lungs. If you had been born in Greece, you would have no difficulty with
the word, for it is Greek for _separation_. It means, in fact, a
_separating partition_, or, as I called it just now, _a floor._ All this
is preparatory to telling you that the liver is hooked to the diaphragm
in the abdomen. It is a very large mass and fills up, by itself alone,
all the right side of the lower compartment, from the top downwards, to
where the bones end which protect the abdomen on each side, and which
are called _the short ribs._ Place your hand there, and you will find
them without difficulty.
Large as the liver is, it hangs suspended to a mere point of the
diaphragm, and shakes about with even the slightest movement of the
body. It is partly on this account that many people do not like to
sleep lying on the left side, especially after a good dinner, because
in this position the liver weighs upon and oppresses the stomach, like
a stout gentleman asleep in a coach who falls upon and crushes his
companion at every jolt of the vehicle. The liver within you produces,
then, the same effect that a cat, lying on the pit of your stomach
would do, and the result is that you have the nightmare.
The liver is of a deep-red color. It is an accumulation of excessively
minute atoms, which, when united, form a somewhat compact mass, and
within each of which there is a little cell, invisible to the naked
eye, where an operation of the highest importance to our existence is
mysteriously carried on. It appears a very simple one, it is true, yet
hitherto it has baffled all attempts at explanation. Listen, however;
the subject is well worthy your careful attention, whether it can be
explained or not, and we must look back to take it up from thebeginning.
I told you about the thousand workmen constantly busied in every part
of our bodies, who call on the blood without ceasing for "more, more."
You will remember further that it is to enable the blood to supply
these constant demands, that we require food.
This being understood, it is not difficult to see why we grow; the
difficulty is, rather, to explain why we do not continue to grow.
Consider, for instance, the quantity of food you have eaten during the
last year. Picture to yourself all the bread, meat, vegetables, fruits,
cakes, &c., piled upon a table. Put a whole year's milk into a large
earthenware pan, all the sweetmeats into a large jar, all the soup
into a great tureen, and see what a huge heap you will have collected
together. Then try to recollect how much you have increased in size
with all this nourishment, which has entered your body. But reckoning
in this way--even supposing the little workmen had used only a half
or even a third of the materials in question, and rejected the rest
as refuse--you would have to stoop in order to get in at the door; and
as for your papa, whose heap must have been bigger than yours, his
case would be desperate indeed; and yet he has not grown at all!
This is very curious, and I dare say you have never thought about it
before.
Do you know the story of a certain lady called Penelope, who was the
wife of Ulysses, a very celebrated king of whom the world has talked
for the last 3000 years--thanks to a poet called Homer, who did him
the honor of making him his hero! The husband of Penelope had left her
for a long time to go to the wars, and as he did not return, people
tried to persuade her to marry again. For peace and quiet's sake, she
promised to do so when she should have finished a piece of cloth she
was weaving, at which she worked all day long. They thought to get
hold of her very soon, but her importunate lovers were disappointed;
for the faithful wife, determined to await the return of her husband,
unwove every night the portion she had woven during the day; and I
leave you to judge what progress the web made in the course of a year!
Now, every part of our bodies is a kind of Penelope's web, with this
difference--that here the web unravels at one end as fast as the work
progresses at the other. As the little masons put new bricks to the
house on one side, the old ones crumble away on another--in this manner
the work might go on forever without the house becoming bigger; while,
on the other hand, the house is always being rebuilt. People who are
fond of building, as some are, would quite enjoy having such a mansion
as this on hand!
At your early age, my love, fewer bricks drop out than are added, and
this is why you grow from year to year. At your papa's age, just the
same number perish and are replaced; and therefore he continues the
same size, although in the course of the year he swallows three times
his own weight of food. But when I say this, do not suppose it is an
offensive remark, or that I think him either too little a man, or too
great an eater; seeing that there are 365 days in the year, and that
a quart of water weighs two pounds: I need not say more!
But the next question is, what becomes of all the refuse which this
perpetual destruction produces?
What becomes of it? Have you forgotten our steward who looks after
everything? He is a more active fellow than I have represented him!
To the office of purveyor-general he adds that of universal scavenger.
But in the latter department he obtains help. Wherever he passes along,
troops of little scavengers press forward, like himself always busy;
and while he holds out a new brick to the mason as he hurries by, the
little scavenger slips out the old one and conveys it away. The history
of these scavengers is a very curious one, and we shall have to speak
about it a little further on. They are minute pipes, _i.e. ducts_,
spread all over the body, which they envelope as if with fine net work.
They all communicate together, and end by emptying the whole of their
contents into one large canal, which, in its turn, empties itself into
the great stream of the blood. Imagine all the drains of a great town
flowing into one large one, which should empty itself into the river
on which the town was built, and you will have a fair idea of the whole
transaction. What the river would in such a case be to the town, the
blood is to the body--the universal scavenger, as I said before. But
you will ask further, What does the blood do with all this?--a question
which brings us back once more to the liver.
You must have seen, just now, that the pockets of our dear steward
would be rapidly overloaded, were he to keep constantly filling them
with the old worn-out materials which the builders rejected, unless
he had some means of emptying them as he went along. Accordingly, a
wise Providence has furnished the body, on all sides, with clusters
of small chambers or cells, in which the blood deposits, as he goes
by, all the refuse he has picked up, and which makes its exit from the
body sometimes in one way, sometimes in another. Now, the cells of the
liver are among these refuse-chambers. One may even consider them as
some of the most important ones. When the blood has run its course
through the lower compartment, I mean the _abdomen_, it collects
from all directions and rushes into a large canal called the _portal
vein_, which conveys it to the liver. As soon as this canal has
entered the liver, it divides and subdivides itself in every direction,
like the limbs and branches of a tree diverging from the trunk; and
very soon the blood finds itself disseminating through an infinity of
small canals or pipes, whose ultimate extremities, a thousand times
finer than the finest hairs of your head, communicate with the tiny
cells of the liver. There, each of the imperceptible little drops,
thus carried into these imperceptibly minute cell-chambers, rids
itself--but no one knows how--of a part of the sweepings it has carried
along with it. Which done, the little drops thread their way back
through other canals as fine as the first, and which go on uniting
more and more to each other, like the branches of a tree on their way
to the trunk--forming at last one large canal, through which the blood
escapes from the liver, once more relieved from its weight of rubbish,
and ready to recommence its work.
You are going to ask me, "What is all this to me--this history of the
blood and its sweepings? It was the bile you undertook to tell me
about, that liquid you spoke of as so necessary for the transformation
of the food: we were to get out of the intestinal tubes by the help
of the bile, you promised me."
Well, my little impatient minx, it is the history of the bile that I
have been relating to you, and what is most remarkable about it is
this. You have perhaps heard of those wholesale ragpickers, who
makelarge fortunes by collecting out of the mud and dirt of the streets,
the many valuable things which have been dropped there? Well, the liver
is the master-ragpicker of the body. He fabricates, out of the refuse
of the blood, that bile which is so valuable in the economy of the
human frame. This bile is neither more nor less than the deposit left
by the little drops of blood in the innumerable minute liver-cells.
See what an ingenious arrangement, and in what a simple way two objects
are effected by one operation!
Now you have learnt the genealogy of the bile, and the double office
of the liver, which benefits the blood by what it takes from it,
benefits the _chyme_ by what it gives it, and is an economist at
the same time--since it only gives back what it has received. This was
what I particularly wished to explain to you: the rest you will easily
learn.
The bile does not make a long stay in the little cells, it also escapes,
by canals similar to those which carry off the blood, after
itspurification; and which in a similar way unite by degrees together,
until at length they terminate in a single canal, communicating with
a little bag placed close against the liver, where the bile accumulates
between the periods of digestion--so forming a stock on hand, ready
to pour at once into the _duodenum_ when the latter calls for its
assistance. The next time the cook cleans out a fowl, ask her to show
you the little greenish bladder which she calls the gall and which she
takes such care not to burst, because it contains a bitter liquid
which, if spilt upon it, would quite ruin the flavor of the fowl. Such,
precisely, is the bag which holds the bile. Moreover, it is close by
the liver of the fowl that you will find it placed: and you can convince
yourself in a moment by it, that the little provision I tell you of
is always stored away therein.
We have also within us a multitude of minute electric telegraphs, which
transmit intelligence of all that occurs from one part of the body to
another, in a more wonderful manner even than the telegraphs of man's
making; later we shall see how they work. By their means the little
bag by the liver is made aware in the twinkling of an eye of the
entrance of the _chyme_ into the _duodenum,_ and forthwith the bile
returns for some distance by the canal which brought it, and then
branches off into a larger one which opens into the _duodenum._
The liver, on getting this intelligence, sets to work more diligently
than ever, and the bile flows in streams into the _duodenum,_ where it
mixes as it arrives with the current which comes from the _pancreas._
Thus combined, the two liquids flow over the _chyme,_ which they
saturate on all sides; and here, as I have said, the work of the
intestinal canal ends. What is serviceable for the blood is separated
from the useless refuse, and nothing remains but to get it out of the
intestines. It is true that in their character of tubes these are closed
on all sides. But do not trouble yourself: a means of escape is
prepared.
Before we part, however, I must apologize for something. I have not
described to you what the bile consists of, or what kind of refuse the
blood leaves in the liver; nevertheless, as you take an interest in
this much-neglected book of nature, you ought to know these things.
It is, however, very difficult to lead you by the hand through so many
wonder*, where the secrets of nature are all in operation at once, and
to explain each as soon as we meet with it. They combine, and progress
together like the waves of the sea, where one breath suffices to agitate
the whole mass.
When we have talked about the lungs, we will have another word to say
about the liver.
LETTER XII. THE CHYLE.
To-day we have to begin by making acquaintance with a new term. I would
willingly have spared you this, if I could, for the word is neither
a pretty, nor a well-chosen one, but we cannot get on without it.
You are aware now that the learned, unknown sponsors, who gave names
to the different parts of the body, bestowed the odd-enough one of
_chyme_ on that pasty substance which passes out of the stomach when the
cooking is over. We have said quite enough about it, and you know enough
of it I am sure. Well! the people seem to have had quite a fancy for the
word _chyme_, for they adopted it again, with only a very slight
alteration, when they wanted to specify separately the quintessence of
the _chyme_ (the useful part that is), which has to unite with the
blood, and which we have been speaking of as the _gold_ of the aliments
--this then they called _chyle_. I give you the name as I received it,
but have no responsibility in the matter.
In concluding the last chapter I said we were sure to find there was
a plan for extracting the best part of the _chyme_, viz. the _chyle_,
from the intestinal canal; and a very simple one it is. A complete
regiment of those little scavengers lately described, are drawn up in
battle-array along the whole length of the small intestine, but
especially round about the _duodenum._ There, a thousand minute pipes
pierce in all directions through the coat of the intestine, and suck,
like so many constantly open mouths, the drops of _chyle_ as fast as
they are formed. They are called _chyliferous vessels_ or chyle-bearers,
just as we might call hot-air stoves _caloriferous_ or heat-bearers--
from the Latin word _fero,_ which means to carry or bear. I mentioned
before that there were, within the intestine, certain elastic valves
which obstruct the progress of the _chyme,_ and oblige it to be
constantly stopping. There are in fact so many of these, and the skin
which lines the intestinal canal is so folded and plaited, that if it
were stretched out at full length on a big table, it would cover at
least as large a surface as that other skin, with which you are so well
acquainted, which entirely clothes the body outside.
Now, the _chyliferous vessels_ we have been speaking of insinuate
themselves into all the plaits and folds alluded to, and thus they
reach at last the very centre of the _chymous_ paste, and not a single
drop of _chyle_ can escape them. They do their work so well, that the
separation is effected long before the paste reaches the large
intestine; and when that has forced its way through the door which
guards the entrance, and which prevents its ever returning again, the
_chyle_ is already far off on its mission. It has threaded its way along
the little pipes, and, always creeping nearer and nearer, is on the
high-road to the heart, where it is anxiously expected.
And what becomes of the rest? There is nothing further to be said about
it, but that it shares the fate of everything else which, having
answered its purpose in its place, is no longer wanted and must be got
rid of. Thus in works where iron-stone smelting is carried on, the
refuse that remains after the ore is extracted, though available for
road-making or other purposes, is thrown out of the manufactory as a
useless incumbrance there.
Our history requires us to follow the fate of that golden aliment the
_chyle,_ which is now in a condition to support the life of the body,
and every drop of which will turn into blood--the blood which beats at
our hearts, nourishes our limbs, and sets at work the fibres of our
brain.
I ought to tell you first that the _chyle,_ when it leaves the
intestine, is very like milk. It is a white, rather fatty juice, having
the appearance, when you look closely at it, of a kind of _whey,_
in which a crowd of globules, or little balls if you prefer it,
infinitesimally small, are swimming about. Some people, whose curiosity
nothing can check, have put the tips of their tongue to it; so I am
able to tell you, if you care for the information, that it has rather
a saltish taste.
At this point it is what may be called new-born blood, and to carry
on the metaphor, blood whose education has yet to be completed. All
the elements of blood are there already, but in confusion and
intermingled, so that they cannot yet be recognised. A wonderful fact,
and one of which I have no explanation to offer you, because among the
many mysteries which are silently going on within us is this, that the
education of the new-born blood begins entirely of itself in the vessels
which are carrying it along. During their very journey, the confused
elements are setting themselves in order and forming into groups. In
short the _chyle,_ when it comes out of the chyliferous vessels,
is already much more like blood than when it entered them, and yet one
cannot account for the change. It is changed, however; its whiteness
has already assumed a rosy tinge, and if it is exposed to the air it
may be seen turning slightly red, as if to give notice to the observer
of what it is about to become.
You know that all our scavengers uniting together deposit their
sweepings in one large canal, which is called the _thoracic duct._
The _chyle_ scavengers arrive there just like the rest, and there
our poor friend finds himself confounded for a moment with all the
dross of the body, as sometimes happens to men who devote themselves
to the public good. But the crisis passes in an instant. A little
further off, the _thoracic duct_ pours its whole contents together
into a large vein situated close to the heart, and the blood has no
difficulty in recognising and appropriating what belongs to him.
Here, my dear little scholar, we conclude the first part of our story.
To eat is to nourish oneself; that is, to furnish all parts of the
body with the substances necessary to them for the proper performance
of their functions. The mouth receives these substances in their crude
condition, the intestinal canal prepares them for use, and the blood
distributes them.
After the history of the _preparation,_ comes naturally that of the
_distribution._
The first is called the DIGESTION. It is the history of the _chyle,_
which begins between the thumb and forefinger while as yet invisible,
hid in the thousand prisons of our different sorts of food, and ends in
the _thoracic duct, when, disengaged from all previous bonds, purified
and refined by the ordeals of its intestinal life, it leaps into the
blood, carrying with it a renewal of life and power.
The second history is that of the CIRCULATION. It is the history of
the _Blood,_ that indefatigable traveler, who is constantly
_circulating_ or describing a circle (the Latins called it _circulus_)
through the body; by which I mean that it is continually retracing its
steps, coming out of the heart to return to it, re-entering it only to
leave it again, and so on without intermission, until the hour of death.
The history of the _Digestion_, which we have just gone through,
goes on quietly from one end to the other without any complication.
That of the _Circulation_, which we are about to begin, is mixed
up with another history, from which it cannot be kept separate while
the description is going on, although the two histories are in reality
quite distinct from each other. The blood describes two circles, to
speak correctly: 1st. A wide one, which extends from the extremities
of the body to the heart, and back again from the heart to the
extremities. 2d. A more contracted one, which goes from the heart to
the lungs, and back from the lungs to the heart. Whilst circulating
in the lungs, it encounters the air we breathe; and here takes place,
between it and the air, one of the most curious transactions imaginable,
without which the blood would not be able to nourish the body even for
five minutes. This is called RESPIRATION, or the act of breathing.
Digestion, circulation, respiration, the three histories together form
but one--that of NUTRITION, or the act of nourishing; in other words,
of supporting life. This is what I called _eating_ at first, that
I might not mystify you at the beginning with hard words. But now that
we are growing learned ourselves, we must accustom ourselves to the
terms in use among learned people, especially when they are not more
formidable than those I have just taught you.
Our next subject for consideration, then, Will be the circulation; and
we will begin with the heart, since that is to the circulation what
the stomach is to the digestion--viz., master of the establishment.
He is a very important person, this heart, as I hardly need tell you.
Even ignorant people speak respectfully of him, and I am sure beforehand
that his history will interest you very much.
Do you feel as I do, my dear child? I am quite happy at having brought
you thus far on our journey, and at being able to take a rest with you
at the gateway of the new country into which we are about to enter,
like travelers sitting down upon a boundary frontier. What a distance
we have come, since the day when I took you by the hand to conduct you
inside this little body, of which you were making use without knowing
anything about it! How many things we have learned already, and how
many more remain to be learned, of which you have at present no idea!
I assure you I should be almost afraid myself of what is before us
yet, if I did not rely upon my own strong desire to instruct you, and
the tender affection I bear to you. Believe me, the greatest of
constraining powers is love; and when I get bewildered in the midst
of some difficult explanation which will not come out clearly, I have
only to place before me those laughing eyes of yours, where sleeps a
soul that must soon awaken to consciousness, in order to make the
daylight come into my own!
Must I add, too, that I am not working for you only? We are all placed
in this world to help each other, and in striving to bring down light
into your intellect, and good sentiments into your heart, I am thinking
also of those to whom you, in your turn, may render the same good
service hereafter, provided I have the happiness of succeeding now
with you. This ought to be so, ought it not? You should resolve to be
numbered one day among those who have not lived altogether for
themselves, but who have given the world something worth having as
they passed through it. To-day's labor will have been well employed
if, later on, it turns out that this history of the _chyle_ has
not been told you in vain!
LETTER XIII.
THE HEART.
There was once upon a time a banker, a millionaire, who could reckon
his wealth not by millions only, but by hundreds of millions and more;
who was, in fact, so tremendously rich that he did not know what to
do with his money--a difficulty in which nobody had ever been before.
This man took it into his head to build a palace infinitely superior
to anything that had hitherto been seen. Marbles, carpets, gildings,
silk hangings, pictures, and statues--in fact, the whole mass of
common-place luxuries as one sees them even in the grandest royal
abodes, fell short of his magnificent pretensions. He was an intelligent
man, and thoroughly understood the respect due to his riches; and the
common fate of kings seemed to him far too shabby for the entertainment
of his dynasty, which he looked upon as very superior to all the
families of crowned heads in the world. In consequence he sent to the
four quarters of the globe for the most illustrious professors, the
most skilful engineers, the cleverest and most ingenious workmen in
every department; and giving them unlimited permission as to
expenditure? ordered them to adorn his palace with all the wonders of
science and human industry.
Science, and human industry, and unlimited means--what will they not
accomplish? No wonder that nothing was talked of for a hundred miles
around but the magic building--of which, by the way, I do not venture
to give you a description, because it would carry me too far away. Let
it suffice to say, that never Emperor of China, Caliph of Bagdad, or
Great Mogul had such a habitation as our banker, and for a very good
reason--he was twenty times as rich as any such gentry as I have named
ever were in their lives.
When all was finished one trifling flaw was discovered: the place was
not supplied with water. A spring-seeker, who was summoned to the
premises, could only discover a small subterranean watercourse, a sort
of zigzag pipe, formed by nature, between two beds of clay, in which
the rain of the neighborhood collected as in a sort of reservoir. The
water was neither very clear nor very plentiful, as you may imagine;
and the professor appointed to examine it, having begun by tasting it,
made a horrible face, and declared there was no use in proceeding any
further; for it had a stagnant flavor which would not be agreeable to
my lord.
To the amazement of every body, my lord jumped for joy when he heard
this unpleasant news. It was proposed to him to fetch water from a
river which flowed a few miles' distance off; but he would hear of
nothing of the sort. What he wanted was something new, unexpected,
impossible--that was his object throughout. He took a pen and drew up
at a sitting the following programme, which caused our poor professors
to open their eyes in dismay:--
1st. We will use the water on the premises.
2ndly. It shall flow night day and in all parts of the palace at once.
3rdly. There shall be plenty of it, and it shall be good.
The professors looked at each other for some time without speaking,
and the gravest of them, whose fortunes and characters had been long
ago established, suggested that they should simply give my lord and
his money the slip, and so teach him to make fools of people another
time!
But the youngsters, less easily discouraged, cried out against this
with one accord. They declared that the honor of science was at stake,
and that they ought to return impudence for impudence, by executing
to the letter the impertinent programme! At length, after much
discussion and many propositions made against all hope, and thrown
aside one after the other as impracticable, a sudden inspiration crossed
the brain of an engineer who had not yet spoken; and the following is
what he proposed:--
What prevented the water from being sweet and fit to drink, was the
want of movement and air. What had to be done, therefore, was to erect
a pump, but a pump provided with numberless small pipes, extending to
the watercourse in all directions, and so arranged that by means of
them it should be able to draw up the water from all the corners and
windings where it lay stagnating, and then forcing it forward into a
pipe terminating in a rose, like that of a watering-pot, whence it
should gush out to fall down in fine rain, into a reservoir in the
open air. From thence another action of the pump was to bring it back
well aerated, to send it once more into a large pipe with numerous
lesser ramifications, which should convey it into every corner of the
palace.
Up to this point all seemed practicable, but the hardest part had not
yet come. The great difficulty was how to supply this enormous
consumption with so slender a runnel of water as the one at their
disposal. But our engineer had provided for this by a stroke of genius.
Under each of the taps (always kept open), which were dispersed all
over the palace, he would place a small cistern, from the bottom of
which should go a pipe communicating with the body of the force-pump
which drew up the water from the original watercourse. By which means
the water which ran from the taps would be taken up again and go back
to feed the reservoir in the open air; whence it would again return
to supply the taps; and so on and on, the same water continually keeping
the game alive, as people call it. Have you not sometimes seen at a
circus or theatre a large army represented by a hundred supernumeraries,
who file in close columns before the audience, going out at one side
of the stage and coming in at the other, following close at each other's
heels indefinitely? By a similar artifice the engineer would change
his meagre little runnel into an inexhaustible fountain. The water
drawn up from the watercourse by each stroke of the pump would fully
compensate for what was used in its passage through the palace by the
inhabitants. Lastly, as it might sometimes happen that the said
inhabitants washed their hands under the taps, the water on its return
to the cisterns, was to pass through a series of small filters, in
order to cleanse it from any impurity it might have contracted by the
way. Always flowing, always limpid, it would soon lose every trace of
its original source, and might defy comparison with the water of any
river in the world!
A unanimous buzz of congratulations welcomed this plan, at once so
simple and so bold, and our professors thought their troubles were
over, but they were not at the end of their difficulties yet. When it
came to the actual erection of the machine, (naturally a most
complicated one, as it had to set a-going a quintuple system of
pipes--pipes from the water-course to the pump, pipes from the pump
to the reservoir, pipes from the reservoir to the pump, from the pump
to the taps, and from the taps to the pump again,)--our banker, who
had got amused and excited as they went on, conducted them to a small
dark closet, only a few square feet in size, concealed in a corner of
the large apartments, and informed them with a laugh that he had no
other place to offer them. Besides which, he made them understand that
on account of its situation, there could be no question of furnaces
or boilers being set up there (he detested equally coal-smoke, fires,
and explosions)--nor of workmen employed about the machine (it would
not be decent to have them going up and down the front staircase)--
nor above all, of the frightful brake-wheels always screeching and
grinding, the unwieldy pistons rising and falling with a noise
sufficient to give one the headache. He himself slept near the little
dark closet, and the slightest noise was fatal to his repose. Having
explained all this, the rich man curtly made his bow and retired.
For once our professors owned themselves beaten. They had come forward
quite proud of their invention, and now they were received, not with
ecstasies of delight, but with fresh demands, more ridiculous even
than the first. They were decidedly being mystified, and were preparing
in consequence to pack up and begone, furious, and swearing by all
their gods that they would never again expose science to see itself
disgraced by a purse-proud vulgarian's scorn; when, lo! happily, a
good fairy, the special friend of learned men, came passing by that
way. She raised her enchanted wand with the tip of her finger, and all
at once a little girl dressed in rags appeared in the midst of our
astonished professors. Without giving them time to recover themselves,
the child put her hand into the little patched waist of her dress, and
drew forth a rounded object, about the size of her closed fist from
which hung a quantity of tubes spreading in all directions.
"See!" cried she; "here is the machine your banker demands of you."
Picture to yourself a small closed bag, narrowing to a point at the
end, and separated within into two very distinct compartments by a
fleshy partition which went across the inside from the top to the
bottom. Such was the object held up by the little girl. Prom each of
these compartments issued a thick tube, ramifying into endless smaller
ones; and they were moreover each surmounted by a sort of pouch, into
which ran another tube, of the same description as the first. Each of
these four portions (the two compartments and their pouches) was in
constant but independent motion, distending and contracting alternately;
and by carefully examining the noiseless play of this singular machine,
(the walls of which were, by the magic power of the fairy, rendered
transparent to the bystanders,) the learned assembly were very soon
enabled to convince themselves, that it fulfilled all the
monstrousconditions exacted of them by the fantastic millionaire.
All was in movement together, I told you; but let us begin at one end.
The right-hand compartment and its pouch represented the first pump;
the pump employed to draw, by the same stroke, the water from the
stagnant channel, and that from the taps. It was perfectly easy to
distinguish the two systems of pipes, and how they united together at
the small pouch on their arrival. When this was distended, a vacuum
was created inside, which was instantly filled by the liquid from the
tube which ran into it, (do not ask me why or how; I will explain that
presently). When it contracted again, the liquid which had just entered
was not able to get back, being prevented from so doing by a very
ingenious and simple contrivance, which requires a brief explanation.
Take off the lock from your chamber-door, which opens inside; then,
standing outside, push against it with your shoulder, and you will get
in without any difficulty. But when you are in, try to push the door
open again with your shoulder in order to get outside into the passage,
and you will find that you will not be able to pass through, and this
simply because it does not open on that side.
Which was exactly what happened to the liquid in the pouch!
The door between the tube and the pouch only opened inwardly, and the
liquid finding itself pressed on all sides in proportion as the pouch
contracted more and more, and unable to return, was obliged at last
to make its way through another similar door which led to the large
compartment below. Here the same game recommenced. The compartment
which had distended itself to receive it, contracted in its turn, and
the liquid finding the road again barred behind it, had no choice but
to force its way through the tube which led to the air-reservoir.
Here commenced the work of the second pump,--the pump of the left
compartment. The little pouch, when distended, was filled by the liquid
from the reservoir, and then forced it forward into the large
compartment below, always by means of the same process. This compartment
again drove it, by a powerful contraction, into the large conducting
tube charged with the office of its general distribution throughout
the body. At the end of all which, it returned once more into the
right-hand pump as before, to pursue the same course again, &c., &c.
Thus, as you see, the whole mechanism turned upon two little points
of detail, of the simplest description possible; namely, first, on the
entrance-doors only opening on one side; and secondly, on the elastic
covers of the pouches and compartments distending and contracting
spontaneously. It was the prettiest thing in the world to see this
unpretending-looking little bag working thus, quite naturally, without
a suspicion that it was solving a problem which so many men, proud of
their science, had given up as hopeless. Certainly here was a machine
which made no noise! Once installed in its dark closet, it would have
been necessary to place your hand upon it to find out that it moved
at all. My lord could certainly sleep beside it without disturbance.
"How much do you want for it?" said they to the poor little beggar
girl. "Name your price; have no fear; we will pay you anything you
wish."
"I cannot give it to you," replied the child; "I need it too much
myself: IT IS MY HEART. Now that you have seen it, make another like
it, if you can." And she disappeared.
It is said that the engineer, who longed to see his idea carried out,
tried hard to construct a similar machine with gutta-percha and iron
wires, and to set it in motion by electricity. But history does not
tell us that he succeeded, and we have yet to ask ourselves whether
the richest man in the world, aided by the wisest men in the world,
could ever provide himself with a miracle of wonder, such as the,
ragged child had received as a free gift from the hands of a gracious
Creator.
LETTER XIV.
THE ARTERIES.
If you have thoroughly understood the story I last told you, my child,
it will have revealed to you the whole mystery of the _circulation
of the blood,_ and you are at the present moment wiser than all the
learned men of antiquity and the middle ages, for they had none of
them the faintest surmise of the truth.
It may, perhaps, seem odd to you that men should have existed for
upwards of five thousand years without making inquiry into a matter
which so closely concerned them, and which was so easy to find out.
Is it not almost incredible that so many hearts should have beaten for
so long a period without any of their owners having felt a wish to
know exactly _why?_ Yet so it is. The action of the heart and the
flow of the blood have not been understood for much more than two
hundred years, and the man whose name is attached to this great
discovery richly deserves that we should say a few words about him.
He was called Harvey. He was an Englishman; physician to King Charles
I., who was beheaded in 1648; and when he first ventured publicly to
teach that the blood was constantly circulating from one end of the
human body to the other, perpetually returning and retracing its steps,
a great scandal was created in the world. He was called a fool,--an
impertinent innovator,--a madman. His words shattered old doctrines,
and he only received for his reward all the petty annoyances which men
are apt to lavish so freely upon any one who tells them something new;
because--do you see?--it is so disagreeable to be disturbed in one's
habits and preconceived ideas.
Harvey is not the only one in the history of mankind who has committed
the sin of being right in defiance of the opinions of his age. It is
true posterity takes account afterwards of the labors of genius, and
inscribes a fresh name upon her list. But one must pay for this glory
in one's lifetime. One cannot have everything at once.
This is an old story, my child, but always new nevertheless; and for
my own part it is, I own, one of my pleasures to amuse myself by
reflecting how much cause for laughter three-fourths of the great men
of the present day are providing for the little girls who shall be
alive two centuries hence. Time is a great avenger, and puts many
things and men in their proper places.
Let us pause here a moment while we are speaking of Harvey. I should
be curious to know what any one of the courtiers of Charles I., bedecked
in feathers, ribbons and laces, would have said to the valet who would
have placed the excellent Harvey, with his insane invention, above his
most gracious majesty, the lord and king of all Great Britain! And yet
what is his most gracious majesty to you to-day? What do you owe to
him? in what does he interest you? While you can never hear the name
of Harvey pronounced without remembering that you are under many
obligations to him! A thousand years hence, when society shall have
made the great progress which may reasonably be expected, the name of
Harvey will be familiar to every one who owns a heart, while that of
Charles I. will be only a vanished shadow; a souvenir lost in the maze
of history.
Our debt of remembrance paid, let us return to the heart--the little
closed bag which labors so prettily. We must now inquire the real names
of whatever has figured in our story.
The two great compartments are called _ventricles,_ the two small
pouches _auricles,_ and they are also distinguished as being on the
right or left side;--_right ventricle, left ventricle, right auricle,
left auricle._
The inner doors on which depends all the action of the machine, are
called _valvelets._ By-and-bye, when the pump and the steam-engine
are explained to you, you will meet again with these treacherous doors,
which never allow what has once entered to go back again; but then we
shall call them _valves._
The air-reservoir, I need scarcely tell you, is the _lung,_ to
which the blood goes to put itself in contact with the air.
The subterranean watercourse, of which I hope we have talked long
enough, is _the small intestine,_ in which the _chyle_ collects; and
the tubes which run into it are, of course, the _chyliferous vessels,_
the only channels by which anything reaches the heart which has not
previously gone out from it.
The tubes of distribution, which run out from the machine in all
directions, are called with us _arteries_; the return tubes, which
bring back the water to the machine, are called _veins._
Finally, we have not exactly the _filters_ employed to clear the
water from the impurities contracted as it goes along, for no such
thing exists in us. There are in our case the refuse-chambers of which
I have already spoken, in connexion with the liver, where the blood
disembarrasses itself of any useless materials, and from which it comes
out with clean pockets, so to speak, reverting to the comparison of
which we have already availed ourselves.
As you see, then, everything comes round again; and the bright idea
which our professors hit upon in order to satisfy the caprice of the
banker is exactly carried out in your own body, only a thousand times
more perfectly than could have been done by them all, even with all
their science added to all his money.
I mentioned that the shrewdest of the party boasted about making an
artificial heart. But, let me tell you, there is one thing I would
have defied him to imitate, by any expedient he could devise, and that
is the inimitable construction of the _arteries_ and _veins,_ and the
incomprehensible delicacy of their innumerable ramifications.
Let us talk a little about these marvellous tubes, and begin with the
arteries, which have the most important part to play.
Did you ever see a doctor try the pulse of his patient? Take hold of
your own wrist and search a little above the thumb. You will soon find
the place and feel something beating against your finger. There is an
artery which passes there, and the little beating you feel is the
rebound of the pulsations, of your heart. Every time that the left
_ventricle,_ by contracting itself, chases the blood into the arteries,
these, of which the tissue is very elastic, become distended all at
once, and then contract again, repeating the process whenever a fresh
gush of blood arrives, so that their movement is exactly regulated by
the movement of the heart. It is true the two movements are in a
contrary direction; that is to say, the artery becomes distended, while
the heart contracts, and contracts when the heart enlarges itself; but
that makes no difference to the doctor. What he wants to know is, with
what force and rapidity the heart of the patient beats, and I will
explain why. It is an interesting point in the history of circulation.
When you were very little--very little indeed, my dear child--your
heart beat from 130 to 140 times in a minute. Afterwards the beats
sank to 100 per minute; then to fewer still. At present I cannot tell
you the precise number: perhaps, about ninety. When you are a grown-up
young lady, it will beat about eighty times in the minute; when you
are a mother, about seventy-three times; when a grandmother (if such
a blessing be granted you), only from fifty to sixty times, perhaps
even fewer. People tell of an old man of eighty-four whose heart beat
only twenty-nine times in the sixty seconds.
Observe that in all my calculations I have taken special care to prefix
the word _about_ to the numbers mentioned. And this because, in
point of fact, the heart is a capricious creature, which has no exact
rules to go by. It changes its pace on every occasion--fear, joy, every
emotion which agitates the soul, quickens or retards its movements;
and derangements of health may be detected by its pulsations, which
are infinitely varied in character. In fever, for instance, which is
nothing but a race of the blood at full speed, the hearts of grown-up
people beat as quickly as those of little children; sometimes, indeed,
more quickly still. In certain maladies it goes with great sudden
leaps, like a galloping horse; in others it trots in little jerks;
while in some cases it moves slowly and wearily, and its throbs are
so weak that one can scarcely feel them.
These pulsations, then, afford important revelations to the doctor.
The heart is for him a gossiping confidant, who lets out the secrets
of illnesses, however closely they may fancy themselves hidden in the
remote depths of the body. When the doctor lays his finger on the
patient's pulse, it is precisely the same thing to him as if he had
laid it on his heart, only with this difference, that the one is much
less difficult to do, and much sooner done than the other.
The artery of the wrist is in fact a small heart, not only because it
follows all the movements of the large one, but because it carries
forward the work which the other begins, and assists also in propelling
the blood to the furthest extremities of the limbs, driving it on in
its turn at each of its own contractions. Imagine a fire-engine, whose
pipes should take up and drive forwards along their whole length the
water which is thrown upon the fire, and you will have some idea of
the marvellous machine which is at work in our behalf within us. Nor
are you to suppose that the wrist-artery is a specially privileged
one, because it has been chosen to hold intercourse with physicians.
All the others are equally serviceable; and if they cannot all be
used for "feeling the pulse," it is because they are generally more
deeply buried in the flesh, where it is not easy to reach them.
Observe your mother when she is packing a trunk, and you will see that
whatever she is most afraid maybe spoiled, she is most careful to put
in the middle, so that it may be least exposed to accidents. And this
is what a kind Providence has done with the arteries, which have the
utmost cause to dread accidents; whilst the veins, which are much
better able to bear rough usage, are allowed to wander about freely
just under the skin. But when the bones happen to take up a great deal
of room, and come near the skin themselves, as is the case in the
wrist, the artery is forced, whether he likes it or not, to venture
to the surface, and then we are able to put our fingers upon him.
And there are others in the same sort of situation; the artery of the
foot for instance. But only just think how far from agreeable it would
be to have to take off your shoe and present your foot to the doctor!
The artery which passes to the temple, just by the ear, is another
affair. That would answer the purpose very well in fact, and I even
advise you to make use of it when you want to feel your own pulse. It
is more easily found than the other even, and its pulsations are still
more easily perceptible. Nevertheless, when all is said and done, it
is better for the doctor to take his patient by the hand than by the
head. Merely as a matter of good manners.
I will now make you acquainted with the principal arteries, and the
manner in which they distribute the blood through the body.
The whole of the blood driven out by the left ventricle at each of its
contractions, passes into one large canal called the _aorta_. The
_aorta_ as it goes away at first ascends; then bends back in a curve;
and from this curve, which is called the _arch of the aorta_ (from its
shape) diverge right and left, certain branch-pipes which carry the
blood into the two arms and on each side of the head; and which are, in
fact, the beginning, or upper end, of those whose pulsations we feel
with our fingers in the two wrists and at the temples.
The supply to the upper part of the body being secured, the _aorta_
begins to descend. But now imagine of what importance it must be, that
this head-artery--the foster-father of the whole body--should be
sheltered from every accident. The _aorta_ once divided, death is
inevitable; you might as well have your head cut off at once; and
thus it has been fixed in the best--that is to say, the safest--place.
Of course you know what is meant by the _backbone_ or _spine_, called
also the _vertebral column_, in consequence of its being made like a
sort of column composed of a series of small bones fastened together,
which are named _vertebrę_. Touch it and feel how solid it is, and how
few dangers there can be for anything placed behind it. Well, that is
the rampart which has been given to the _Aorta_. As this descends, it
slips behind the heart and takes up its place in front of the _vertebral
column_ which it follows all the way down the back, just to the top of
the loins. There it is, so to speak, almost unassailable; in fact hardly
any cases are known of the _Aorta_ being wounded; to get at it, it would
be necessary to bestow one of those blows which used to be given in the
time of the Crusades, which cut the body in two. There was an end of the
_Aorta_, as of every thing else then; it was unfortunately not worth
talking about any longer!
The next time you see a fish on the table, ask to be shown the large
central bone. It is the fish's _vertebral column_, and it will give you
an idea of your own, for it is constructed on the same plan. You will
perceive a blackish thread running all along it--that is _the aorta_.
As it descends, the _aorta_ sends off on its passage a great number of
arteries which carry the blood into all parts of the body. Arrived at
the loins it forms a fork; dividing into two great branches, which
continue their descent, one on each side the body, down to the very
extremities of the two feet.
As you perceive, dear child, this is not very difficult to remember.
A large fork, whose two points are at the tips of the feet, the handle
of which curves at the top like the crook of a crozier; from this curve
come four branches, which pass into the two arms and to the two sides
of the head--and this is the whole story. But of course, it would be
another affair were I to enter into the detail of all the ramifications.
Here it is that all engineers, past, present, and future, are baffled,
defeated and outdone! Choose any place you please upon your body, and
run the finest needle you can find into it what will issue from the
puncture?
"Thanks for the proposal," you say; "I have no occasion to try the
experiment, to discover that blood will come out."
You say that very readily, young lady; but have you ever asked yourself,
what is implied by your being so sure before hand that you can bring
blood from any part of your body if you choose to prick it, though
never so slightly? It implies that there is not on your whole frame
a spot the size of a needle's point, which has not its own little canal
filled with blood; for if there were such a one, there at any rate the
needle would pass in without tearing the canal, and causing the blood
to flow out. And now count the number of places from the top to the
bottom of your dear little self, on which one could put the point of
a needle, and even when you have counted them all, do not fancy you
have arrived at the number of the tiny tubes of blood. Compared to
these, your needle is a coarse stake, and tears not one but a thousand
of these little tubes in its passage.
That seems to you rather a strong expression, does it not? But let me
make good my boldness. A needle's point is very fine, I admit; but a
person who could not see it without spectacles must have very poor
sight. Whereas the last subdivisions of the blood-tubes are so
attenuated, that the best eyes in the world, your own included, cannot
distinguish them. You are astonished at this, and yet it is nothing
compared to what follows.
No doubt you have heard of the microscope,--that wonderful instrument
by which you may see objects a thousand, a hundred thousand, a million
times, if necessary, larger than they really are. With the microscope,
therefore, as a matter of course, we can see a good many of those tiny
canals which elude our unaided sight. But, alas! we discover at the
same time that these are by no means the last subdivisions. The canals
invisible to our naked eyes subdivide themselves again into others,
and these into others again, and so it goes on, till at last--the man
at the microscope can see no more, but the subdivisions still continue.
You were ready to exclaim, at my talking of thousands of canals being
torn by a needle in passing through; but had I even said millions, it
may be doubted whether I should have spoken the whole truth.
Besides, when you consider the office of the blood, you can easily
understand that if there were a single atom of the body left unvisited
by him, that atom could never be nourished. Do I say nourished? I have
made here a supposition altogether inadmissible; it could have no
existence at all, since it is the blood only which produces it.
These imperceptible canals of blood have been called _capillaries_,
from the Latin word, _capillus_, which means a hair; because the
old learned men, who had no suspicion of the wonders hereafter to be
revealed by the microscope, could think of no better way of expressing
their delicacy, than by comparing them to hairs. Very likely they
thought even this a great compliment, but your delicate fair hairs,
fine as they are, are absolute cables--and coarse cables too, believe
me, compared to the _capillary vessels_ which extend to every portion
of your body.
Observe further, that each of these arterial _capillaries_ is
necessarily composed (being the continuation of the large ones) of
three coats enclosed one within the other, which can be perfectly
distinguished in arteries of a tolerable size; add to this that within
these coats there is blood, and in the blood some thirty substances
we know of, not to speak of those we do not know; and then you will
begin to form some notion of the marvels collected together in each
poor little morsel of your body, however minute a one you may picture
to yourself.
LETTER XV.
THE NOURISHMENT OF THE ORGANS.
When I said formerly that our dear and wonderful steward the blood,
was everywhere at once, you little suspected the prodigies involved
in that _everywhere_. But you will have a glimpse of them now, when I
tell you it is at the extremities of the _capillary arteries_ that he
carries on his distribution of goods, and accomplishes a mysterious act
of nutrition; a wonder much greater even than that of which we have just
spoken. Here, indeed, the question is no longer mechanical divisions,
whose delicacy, surprising as it may be, is yet within our powers of
comprehension. What is more surprising still, what moreover we cannot
comprehend at all, is the delicate sensitiveness of tact--I would almost
say of instinct--with which each one of the million millions of tiny
atoms of which our body is composed, draws out of the blood--the common
food of all--exactly that aliment which is necessary to it, leaving the
rest to his neighbor, and this without ever making a mistake.
You have never thought about this; for children go on living at their
ease, as if it was the simplest thing in the world to do; never
suspecting even that their life is a continued miracle, and never, of
course, therefore, feeling bound to be grateful to the Author of that
miracle. And alas! how many hundreds of people live and die children
in that respect.
But what would happen, I should like to know, if the eye took to seizing
upon the food of the nail, if the hairs stopped on the way what was
intended for the muscles, if the tongue absorbed what ought to go to
the teeth, and the teeth what ought to go to the tongue! Yet what
prevents their doing so? Can you tell me? They all drink alike out of
the same cup. The same blood goes to furnish them all. The substances
that it brings to the eye are the same as those which it brings to the
nail; and nevertheless the eye takes from it that which makes an eye,
and the nail that which makes a nail.
How is this done, do you think? that is the question.
When the doctors reply to this, that each organ has its peculiar
sensibility, which makes it recognize and imbibe from the blood one
particular substance and no other, they are strangely mistaken if they
flatter themselves that they have really answered anything. They have
done nothing but reproduce the question in other words, for it is
precisely that sensibility which requires explanation, and to tell us
that it exists, does not explain much, you must own. If you were to
ask why you had got a headache, and some one were to reply that it was
because your head ached, you would not be much the wiser I fancy.
Each of our organs, then, may be considered as a distinct being, having
its separate life, and its particular likings. These organs behave
towards the blood like men who recognize some friend in a crowd, and
proceed to seize him by the arm; and when I told you just now that
they never made a mistake, I spoke of their regular course of action
in ordinary circumstances. Like men, they also make mistakes sometimes,
in certain cases; and take one substance for another, or do not
recognize the one they are in need of; an unanswerable proof that at
other times they exercise a sort of discernment, and do not act by a
sort of fatality, as one might be tempted to believe. Look at the
bones, for instance. They are composed of _gelatine_ (which cooks
serve up under the name of meat-jelly, but which would be more properly
called bone-jelly), and of phosphate of lime, a kind of stone of which
we have spoken before, if I remember rightly, and from which they get
all their solidity. Originally, the substance of the bone is entirely
gelatinous, and the phosphate of lime deposits itself therein by
degrees, as time goes on, and always in greater abundance as we advance
in age.
Properly the bones borrow only gelatine and phosphate of lime from the
blood. But when they come to be broken, their texture or _tissue_
inflames in the fractured place; and then it changes its tastes, if
I may so express myself; and, lo and behold, extracts from the blood
that which forms certain little fleshy shoots, which unite together
from the two sides of the fracture, and so mend the broken bone. Here is
one exception to the rule.
Again, in certain diseases, the bones suddenly quarrel with the
phosphate of lime; they will not hear of it any longer, they will not
accept a fresh supply; and as the old wears out by degrees, by reason
of the continual destruction of which I spoke the other day, the bones
become more and more enfeebled, and soon can no longer support the
body. A second exception this.
Finally, when old age comes on, the bones end by being so much
encumbered with phosphate of lime, that they have no room to admit the
fresh supply which keeps coming to them in the blood. What becomes of
it then? It goes to seek its fortune elsewhere; and there are charitable
souls, who forgetting their instinctive antipathies, consent to give
it hospitality, though much to the prejudice of the poor old man
himself, who is no longer served so well as formerly, by the incautious
servants who have allowed themselves to be thus fatally beguiled; but
no one consults him. It is the arteries especially, and sometimes
the muscles, which take this great liberty, and it is not unusual among
old people to meet with these fairly _ossified_--that is to say,
changed into bone, thanks to the phosphate of lime with which they
have consented to burden themselves. This is a third exception, and
I will spare you any others.
What may we infer from all this, my dear child? Well, two things.
First, that we know nothing at all about the whole affair; a fact which
at once places us on a footing with the most learned philosophers in
the world. Secondly, that our body is a perpetual miracle; a miracle
which eats and drinks and walks, and which we must not look down upon
for so doing: for God dwells therein. I should have to come back to
this at every turn, if I wanted to fathom everything I have to tell
you about. Each tip of hair which you grow, is an incomprehensible
prodigy which would puzzle us for ever, if we did not call to our aid
those eternal laws which have made us what we are, and to which it is
very just our spirits should submit, since we could not exist for one
second were they to cease from making themselves obeyed in our bodies.
Reflect on this, my dear little pupil. Young as you may be, you can
already understand from it, that there is above you something which
demands your respect. The good God, to whom your mother makes you pray
every night, on your knees, with folded hands, is not so far off as
you might perhaps suppose. He is not a being of the fancy, secluded
in the depths of that unknown space which men call Heaven, in order
to give it a name. If His all-powerful hand reaches thus into the
innermost recesses of your body, His voice speaks also in your heart,
and to what it says you must listen.
LETTER XVI.
THE ORGANS.
Contrary to my custom, my dear child, I made use, in the last chapter,
of a new word, without giving an explanation of it.
I spoke to you of _our organs_, and we have not yet ascertained what an
_organ_ is.
You probably knew what I meant, because it is a word which is used in
conversation and pretty well understood by everybody. But I am bent
upon giving you a more exact idea of it, for the trouble will be well
bestowed. If I did not do this at once it was because there is a good
deal to tell about, and that would have carried me too far away from
my subject.
_Organ_, comes from the Greek word _organon_, and means _instrument_. It
was used particularly to signify instruments of music, so much so that
our word "organ" comes from it. Our bodily organs then, are
_instruments_, or _tools_ if you like it better, which have been given
to us, wherewith to perform all the acts of life; and as there is not
one part of the body which is not of use to us for some purpose or
other, our body is, in point of fact, from head to foot a compound of
_organs_. Thus the hand is the tool which we make use of to lay hold of
anything--so an _organ_; the eye is the instrument of sight--so an
_organ_; the heart is the machine which causes the blood to circulate--
so an organ; the liver fabricates the bile--it is an organ therefore;
the bones are the framework which support the weight of the body--so
organs; the muscles are the power which sets the bones in movement--
organs also, therefore; the skin is the armor which protects them--so an
organ: in fact everything within us is an organ. If there was any corner
of our body which was not an organ, it would be useless to us, and we
should not, therefore, have received it, because God makes nothing
without a use.
Here lies the secret of that great miracle which is called life. I do
not know whether you will be able to understand me thoroughly, but
open your ears, as if some one was going to explain addition to you;
this is not more difficult.
Life is in reality the total of an addition sum. Each one of our organs
is a distinct being which has its particular nature and special office;
its separate life consequently; and our individual life is the sum
total of all these lesser lives, independent one of the other, but
which nevertheless blend together by a mysterious combination, into
one common life, which is everywhere and nowhere at the same time. It
follows from this, that the more organs a being has, the greater is
the sum total; the more, consequently, is life developed in him.
Remember this when we begin to study life in the lower animals. In
proportion as you find the number of _organs_ diminish, you will
find life diminishing in power, until we arrive at beings who have,
as it were, only one organ apparent, and whose life is so insignificant,
that we have some difficulty in giving an account of it, and are saying
the utmost that can be said in calling it life at all.
But this comparison of life to the total of an addition sum, is too
dry; and, although it has its appropriate side, yet it might give you
a false idea of life; which is what always happens when one tries to
solve inscrutable questions and hidden mysteries by a matter-of-fact
illustration.
Let us try for something more to the purpose.
I told you that the Greek word _organon_ was applied especially
to instruments of music. Well, let us consider our organs as so many
musical instruments. You have, probably, sometimes been at a concert.
Each of the instruments in the orchestra performs its own part, does
it not? The little flute pipes through all its holes; the double-bass
pours thunder from its chords: the violin sighs with his; the cymbals
clash; the Chinese bells dance to their own tinkling; all go at it in
their own fashion, each independently of the other. And yet, when the
orchestra is in good tune together, and well played, you hear but one
sound; and to you the result of all these various noises, each of which
would have no meaning alone, is music composed by some great artist
whom you do not see. It is no longer a flute, a double-bass, or a violin
which you hoar; it is a symphony of Beethoven's, an oratorio of Haydn's,
or Mozart's overture to _Don Juan_.
Life is just like this. All the instruments are playing together, and
there is but one music; music written by God.
But wait! when I say _life is just like this_, let us come to an
understanding. Life is _some_thing like it, that is all, for as
to telling you what life is, I shall not attempt it. I know nothing
about it, do you see, though that is a painful confession to have to
make to a pupil; but in this case it does not distress me, and you are
welcome to hunt the world through for a master, who in this matter
does know anything. I could make a hundred other comparisons, but
theywould all fail in some point or other. Shall I tell you where this
one fails? In an orchestra there is always a musician by the side of
the instrument. Now with us we see the instrument well enough, but we
cannot see the musician.
You are inclined to ask me, perhaps, why I am wasting so much paper
to-day in talking to you about organs, instead of going on tranquilly
with our little history of the circulation. But I told you just now
that the secret of life lies in the organs, and before entering upon
the history of life, I ought to have begun with them. It is there all
the books begin which treat of the subject we are studying together,
and if you had one in your hands at this moment, it would teach you
that all creatures whatsoever are divided into those which have organs
and those which have none--that is, into _organic_ and _inorganic_
beings [Footnote: A lump of iron is the same throughout. Each of its
parts has the same properties and the same uses. It has no organs, it is
an _inorganic_ being. A rose tree has flowers, which are differently
made from its leaves, and serve a different use: a root which sucks up
the precious food of the earth; a bark which is of a different nature
from the wood, and serves a different purpose. It has organs; it is an
_organic being_: all animals and vegetables are _organic beings_.] (_in_
stands here for _not_, as _in_complete means not complete).
This is, in fact, the starting point for the study of nature, and there
are many other things besides which I ought to have told you before
I began. But we went straight ahead, without looking at what we were
leaving behind, satisfied with turning aside from time to time to pay
our debts.
And while I am making my confession, I ought to tell you all. You would
probably only have listened to me with half an ear, if I had begun at
the beginning. There is a proverb which says--"The appetite comes with
eating." I do not advise you to follow this proverb too closely at
dinner, for it might mislead you sadly. But it is always true when
applied to learning; it is what one knows already that gives one a
taste for learning more. If I have been making you bite at the organs
to-day, which is rather a tough morsel, it was because I fancied that
your appetite had begun to come. Was I wrong?
Let us now return to the blood which nourishes the organs.
LETTER XVII.
ARTERIAL AND VENOUS BLOOD.
It is at the extremity of the capillary arteries, as we have said,
that the incomprehensible prodigy of the nourishment of our organs is
accomplished. This done, the next thing is for the blood to return to
its starting-point; and here recommence those infinitesimally minute
wonders of which we have already spoken. Close upon the capillary
_arteries_ follow the capillary _veins_, equally fine and imperceptible
as the others. These take possession of the blood everywhere at once,
without allowing it a moment's respite, and it is thenceforth on its
road of return, travelling back again to the heart.
Where do the veins begin? where do the arteries end? No one can say
precisely, since the last ramifications of each elude the eye of man,
however much it may be aided by the admirable instruments which his
genius has invented. Nevertheless, although no one has ever ascertained
the fact by sight, there is one thing I can tell you--namely, that our
minute veins are a continuation of our minute arteries, and that it
is the same canal which as it lengthens out turns from an artery into
a vein, without any interruption; the substances destined for the
nourishment of the organs passing through its walls, as moisture passes
through our skin when we perspire.
But if nobody has seen this, say you, how can they know it for a fact?
Let me explain. In man, and in the animals which come nearest to man
in structure, it has never been seen; but it has been seen elsewhere.
This requires a little explanation, and you will not regret my giving
it hereafter. It has its interest, I assure you.
When you put your hand on your throat, how does it feel to you?
_Warm_, does it not? And when you take hold of a kitten or a bird,
how do they feel? _warm_ in the same way. Now, then, can you tell
me whence comes this warmth? But to save time I will answer the question
myself. It comes from their and your _blood_, which is itself warm, and
we shall soon see why. You have no idea of all the curious facts wrapt
up in that little phrase, "You are warm-blooded;" your blood is warm.
But it has not got warm of itself; bear that well in mind.
Now if you touch a frog, a lizard, or a fish, how do they feel to you?
Cold, of course, you answer. But I ask why? A question you will answer
in the same way as the other. Because their blood is cold, they are
"cold-blooded."
Precisely; and while you are about it you may add that, if their blood
be cold, it is because it has not been warmed as yours is. Do not be
impatient, we shall make all this clear at the proper time and place.
Now in the cold-blooded animals, such as serpents, frogs, tortoises,
lizards, fishes, and others, the blood circulates as it does in us,
and what is more, it does so, thanks to a machinery very similar to
our own. But, as you may imagine, a machine which produces warmth must
be constructed in a more perfect manner than a machine which produces
no warmth; and to speak truth, without flattering you, there is a
little difference between you and a frog, and it seems natural enough
that the body of a frog should be more clumsy in structure than yours.
It is the old story of the poor man being not so well lodged as the
rich; but putting aside rich and poor, who are all human beings alike,
let us take one of those lovely dolls who walk, and move their arms
and head, and say papa! and mamma! and compare it with a cheap bazaar
doll which you can get for a penny. Both are made, in the main, in one
way. Each has two arms, two legs, a mouth, a nose, eyes, &c.; but what
a difference in the details of the two! and what infinitely more pains
have been bestowed on one than on the other!
Well, cold-blooded animals are, so to speak, _penny doll_ animals,
by comparison with ourselves. Like us they have arteries and veins,
but there is not near so much workmanship in them; and that marvellous
delicacy of the capillary extremities, which in man and in the
warm-blooded animals drives the close observer to despair, does not
exist to trouble us in these others. It is true that with the naked
eye we are still unable to see everything, even in them; but with the
help of the microscope the whole is laid open to us--the extremities
of the arteries and the extremities of the veins; and it was here that
what I was telling you of, just now, was observed and discovered,--
namely, that the end of the artery changes into a vein, without any
interruption in the tube. It was these very observations upon fishes and
frogs, which eventually gained the day in favor of Harvey's ideas on the
circulation of the blood, at which the learned men of his own age had
laughed so much. He was dead by that time it is true, as has happened
but too often in such cases, but do not let us pity him too much! He who
has had the rare good-fortune to lay hold of a new truth, and launch it
into the world, is sufficiently recompensed in advance. If he also
craves after the flattering voice of man's approbation, and the toylike
pleasure of personal triumph, he is after all but a child, unworthy of
the great part God has given him the privilege of playing.
A child, did I say? Then how rude you must have thought me, dear child!
And as a punishment, you are perhaps going to remind me that I have
once more fallen into my old bad habit of wandering away from my
subject. Never mind, I am going to return to it at once.
How can one distinguish--you will ask me--an artery from a vein, so
as to be able to determine which is a vein and which an artery?
In many ways, I reply. First of all, an artery, as I told you lately,
is composed of three coats, of which the principal, _i.e._. the
inner one, is tough and elastic, whereby the artery is enabled to force
the blood forward in its turn, but which is also the reason of arterial
cuts being so dangerous; for in such cases the wounded tube remains
wide open; being held so by the stiffer inner coat; and thus the blood
is allowed to run out indefinitely. Now this inner coat is wanting in
the veins, whose walls sink in together when a cut is made in them,
so that it is much easier to stop the flow of the blood in them.
Furthermore, the veins are furnished inside at intervals with little
doors, similar to those we noticed at the entrance of the _auricles_ and
_ventricles_ of the heart. You remember those important _valvelets_, on
which depends so much of the mechanism; which permit the blood to pass
in one direction, but will not allow it to return back in the
other?--well, the little doors of the veins, which are also called
_valvelets_, do exactly the same work. They open in the direction of the
heart, to allow the blood to pass on, but it finds them fast closed if
it wants to go back; so that as soon as it has forced one passage there
is no longer any hope of its return, and thus by degrees it gets nearer
and nearer to the heart without any possibility of escape. There is
nothing similar to this in the arteries, which the blood traverses in a
single bound from the impetus it receives from the heart.
Finally--and this is most important--the blood which is found in the
veins is no longer the same as that which fills the heart.
No longer the same? you exclaim--have we then two sorts of blood in
our bodies? Most certainly, my dear child; but you would not have
suspected it; for when you accidentally prick or cut yourself, or when
your nose bleeds, it is always the same sort of blood that comes
out--that fine red liquid which everybody knows so well by sight. This
is because the blood flows at once from the small arteries and small
veins, and what you see is a mixture of the two. The same mixture
issues from all wounds, whether small or great, and on this account
people are unanimous in declaring that blood is red; a statement which
is not true of either arterial or venous blood, separately. The last
is black, as you might convince yourself if you had courage enough,
and should happen to be in the room with any one who was going to be
bled,--a rare event, happily, in these enlightened days.
In such a case it is always a vein which is opened, the reason of which
you will understand, after what I said of the danger of cutting the
arteries. You would there, fore see a reddish black jet of liquid spout
from under the lancet; much blacker than red, however--that is
_venous_ blood. When, on the other band, an artery has been accidentally
cut, what comes out is quite different. It is a rosy, frothy fluid,
almost like milk and carmine dissolved in it, which has been whipped up
with a stick; this is called _arterial_ blood.
Nothing is more simple, as you perceive, than to distinguish an artery
from a vein; you have only to ascertain what is inside of it. When the
blood goes out to our organs to nourish them, it is _arterial_; when it
is returning back after having nourished them, it has become _venous_.
But what--you will ask--is it going to do now at the heart, towards
which it is on its road? It is going to seek there a fresh impetus which
shall send it once more into the lungs, where it will again become
_arterial_, _i. e._ and once more capable of affording nourishment to
the organs. Therein lies the whole secret, and the why and the wherefore
of the CIRCULATION.
This is easily said, dear child; but suppose that you do not comprehend
it? Well, you need not be ashamed. There is no possibility of
comprehending it until one has learnt what RESPIRATION is--so here we
are stopped short.
To-morrow, then, when we will begin with the study of this third part
of the History of Nutrition; and if the first two have amused you, I
feel pretty sure you will not find this last one dull.
LETTER XVIII.
ATMOSPHERIC PRESSURE.
When we have been laboring very hard, my dear child, and want to rest
for a minute, we say, _Let us take breath_; because breathing is
an action which takes place of itself, requiring neither effort nor
attention on our part.
But, if it takes place of itself, it does not explain itself;
consequently, when I say to you, _Now, let us take breath_, this
is not a signal for my having a rest, for I have undertaken to explain
Respiration to you.
If you were a German, I would remind you of what so often happens when
you put a fork into a dish of sour-krout. You want to lay hold of a
little bit merely, but the strips of cabbage-leaf are twisted one
within the other, and hang together in spite of you, so that
withoutintending it you get hold of a whole plateful at once.
Now this Respiration affair is something like the sour-krout
story--begging your pardon for the comparison. I should have liked to
give you only a small plateful--a child's plateful--of it; but I feel
the explanations coming, hanging one upon the other; and, whether I
will or no, I must treat you like a grown-up person, and we must give
up for once the nice little doll's dinners with which we began.
In my opinion, you will lose nothing by the change if you will but pay
attention; for about that soft little breath of yours, which is always
coming and going over your pretty lips, there are many more things to
be learnt than you have heard of yet. As I said just now, you will
find you have got hold of a plateful all at once. A good appetite to
you!
To prevent confusion we will divide the subject into two parts. I shall
explain to you first, _How we breathe?_--a very curious question,
as you will see. And afterwards we will examine, _Why we breathe?_--
which is still more interesting.
First, I must tell you that air is heavy, and very heavy too; a thousand
times more so than you may suppose. The air we breathe, through which
we move backwards and forwards, that air is _some_thing, remember,
although we do not see it; and when there is a wind, that is to say,
when the air is in motion, like a stream of water running down a hill,
we are forced to acknowledge its being something, for we see it throw
down the largest trees and carry along the biggest ships. But without
going so far out of the way for examples, try--you who run so well--to
run for two minutes against a strong wind: and then you shall tell me
whether the air is something or nothing. But if it be something it
must have weight, for all substances have; paper as well as lead; with
this sole difference, that the weight of lead is greater in proportion
to its size than that of paper. Now a sheet of paper is very light,
is it not? and you would be puzzled perhaps to say what it weighs. But
many sheets of paper placed one upon the other, end by forming a thick
book which has its undeniable weight; and if some one were to heap
upon your head a pile of large books, like those you see on your papa's
shelves, the end might be that you would be crushed to death.
In the same way, a small amount of air is by no means heavy; but you
can conceive that a great quantity of it gathered together may end by
weighing a great deal. Now get well into your head the fact, that we,
here, on the surface of the earth, are at the bottom of an immense
mass of air, extending to somewhere about forty or fifty miles above
our heads. Let us say forty to make more sure, for learned men have
not yet been able to calculate the precise height to a nicety; and for
my own part, I think we have done wonders to get so near the mark even
as this. But can you picture to yourself the distance which forty miles
high really is? I will help you to form some idea.
One mile contains 5,280 feet, and your papa is six feet high. One mile
high would therefore be 880 times as high as your papa, But this is
a mere nothing--only one mile's height. In forty miles there would be
no less than 211,200 feet; and setting papas aside, of whom it would
take 35,200, one on the top of the other, to go so far into the sky,
let us think of the height of the tallest buildings you know; church
and cathedral towers for instance. Now the towers of many parish
churches are 150 feet high; the towers of York Minister not 300. At
that rate it would take 1,408 ordinary parish church-towers, or upwards
of 704 York Minster towers, piled one above the other, to reach to the
end of the forty miles of air above our heads. I leave you to judge
what would be the weight of a mass of paper piled up as high as that.
You may safely grant then, that this mass or pile, or if you like it
better, this _column_ of air (for that is the proper expression),
must be of considerable weight; as is still further made certain by
the fact of its having been weighed, so that I can even name the weight
to you if you wish to hear it. Bear in mind too, that the weight of
a column of air will be in proportion to its _superficial extent_--to
its breadth and width, that is; for, as you may suppose, a column as
large in extent as one of the towers of York Minster will weigh a good
deal more than one the size of a single brick.
But wait; here is a book on the table which will serve me for a measure,
and as you will probably find the same on your mamma's table, you can
follow my measurement. It is a French Grammar. The back is seven inches
long and four and a quarter wide. That is, there are four and a quarter
rows, each seven inches long. In other words, the back contains
nearly--and let us call it quite, for convenience' sake--thirty inches
side by side. Thirty _square inches_ as it is called. Measure your
mamma's copy and you will see. Now, can you guess the weight of the
column of air forty miles high which this volume supports? Upwards
of four cwt.; 450 lbs., that is to say. If you want to be very exact,
here is the rule. Air presses on all bodies at the rate of fifteen
pounds to every square inch; so now you can make the calculation for
yourself.
But I suspect you had no idea you were so strong; for I see you tossing
up the book, heavily laden as it is, like a feather.
Comfort yourself. There is no magic in the matter. If a very strong man
were to push you on one side, could you resist him? Certainly not. But
if another man of equal strength were to push you at the same time on
the other side, what would happen? Well, you would remain quietly in
your place, without troubling yourself more about one than the other,
the two forces mutually destroying each other. And this is the case
here. While the air above your book is weighing down upon it with a
force of 450 lbs., the air below it presses against it underneath with
an equal weight, and this destroys the effect of the other. From 450
lbs. take 450 lbs., and nothing remains. Your grammar has nothing to
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