We have spent a very long time, my dear child, over the little fire,
which goes on burning secretly in every one of us, quietly devouring
what little girls eat with such a good appetite, quite unsuspicious
of what they are doing it for. However, if I mean to finish the history
of our mouthful of bread, I must push on to its last chapter.
The _whole_ of what we eat is not burnt, as you may easily suppose; for,
if it were, what would the blood have left to feed the body with, and to
repair in due proportion the continual destruction or waste which goes
on in our organs? Our food, or "_aliments_" as the general collection of
different sorts of food is called, are divided into two very distinct
sets: some, which are destined to be burnt, and which are called
_aliments of combustion_; others, which are destined to nourish the
body, and which are called _aliments of nutrition_. I have to tell you
now about these last, and you will find their history by no means
uninteresting.
Learned men having detected, beyond the possibility of a doubt, the
existence of these two sorts of aliments, one is tempted to think they
ought to have made it known to the cooks, and that ever since so
important a discovery, the dishes on all well-regulated tables should
have been arranged accordingly; aliments of combustion on one side,
aliments of nutrition on the other. It cannot be enough merely to give
your guests a treat; you ought to provide them with everything necessary
for the proper fulfilment of the claims within; and if you give some
nothing but combustibles, leaving the others no share of fuel, how
will they be able to manage? Nobody thinks about this, however; not
even cooks, to begin with, who, as far as fire is concerned, find they
have had quite enough to do with it in their cooking; and as for the
guests, when they have had their dinner they go away satisfied, as a
matter of course, quite as well provided for as if the mistress of the
house had made her calculations, pen in hand, while writing out the
bill of fare, with a view to combustion and nutrition. Now, how is
that?
It is because the two sorts of aliments are, for the most part, met
with together in everything we eat, so that we swallow them at once
in one mouthful; and have therefore no need to trouble ourselves further
on the subject. There is our bit of bread, for instance. What is bread
made of? Of flour. Bread, then, must contain all that was previously
in the flour. Very good. Now I will teach you how to discover in flour
the aliment of combustion on the one hand, and the aliment of nutrition
on the other.
Take a handful of flour, and hold it under a small stream of water;
knead it lightly between your fingers. The water will be quite white
as it leaves it, carrying away with it a fine powder, which you could
easily collect if you were to let the water run into a vase, where the
powder would soon settle to the bottom. That powder is starch--the
same starch as washerwomen use for starching linen, and which our
grandfathers employed in powdering their wigs. You had some put on
your own hair one day when you were dressed up as a court-lady of olden
time. Now, starch is an excellent combustible. People have succeeded,
by means which I will not offer to detail here, in ascertaining almost
exactly what it is made of, and they have found in it three of our old
acquaintances, oxygen, hydrogen, and carbon, combined together in such
proportions that 100 ounces of starch contain as follows:
Ounces.
Carbon 45
Hydrogen 6
Oxygen 49
---
100
I give you the calculation in round numbers, so as not to burden your
memory with fractions; and I will do the same with the other sums I
shall have to go through to-day, this being, let me tell you, an
arithmetical day. Besides, I could scarcely take upon myself to warrant
the absolute correctness of those very precise fractions people
sometimes go into. Even our learned friends squabble now and then as
to which is right or wrong over the 100th part of a grain, more or
less, in making out their balance, and you and I will not offer to
decide between them. I always think we have accomplished wonders in
getting even _near_ the mark, and with their permission we will
stop there.
Starch, then, of whose weight carbon constitutes nearly one-half, is
of course a first-rate combustible. Indeed, one may almost consider
it the parent, as it were, of at least half our aliments of combustion,
for if (in consequence of a certain operation, which nature has the
power of performing for herself, in certain circumstances) it loses
a portion of its carbon, so that there remain but 36 ounces of it in
the 100 of starch, our starch is turned into something else; now can
you guess what that something is? Neither more nor less than _sugar_!
Witness the grand manufactories at Colmar, in France, where bags of
starch are converted into casks of syrup by a process of nature alone;
so that the inhabitants of the neighborhood sweeten their coffee at
breakfast with what might have been made into rolls, had it been left
alone. And this is not all. Give back this starch-sugar into the hands
of Nature once more by putting it into certain other conditions, and a
new process begins in it. About a third of its carbon will unite itself,
of its own accord, with the two-thirds of its oxygen, so as to make
carbonic acid, (you are acquainted with that gentleman now) which shall
fly off and away, and there will remain--what do you think?--_Alcohol_,
that other combustible we talked about, and which burns even better than
sugar and starch, since in a hundred ounces it contains as follows:--
Ounces.
Carbon 53
Hydrogen 13
Oxygen 34
---
100
All this astonishes you. What would you say then if I were to tell you
that your pocket-handkerchief is composed of entirely the same materials
as starch, and in the same proportions too, and that if a chemist were
to take a fancy, by way of a joke, to make you a tumbler of sugar and
water, or a small glass of brandy out of it, he could do so if he
chose. Wonders are found, you see, in other places besides fairy tales;
and since I have begun this subject I will go on to the end. Know then
that from the log on the fire, to the back of your chair, everything
made of wood, is in pretty nearly the same predicament as your
pocket-handkerchief; and if people are not in the habit of making casks
of syrup and kegs of brandy out of the trees they cut down in the
woods, it is only, I assure you, because such sugar and brandy would
cost more to make than other sorts, and would not be so good in the
end. Should some one ever invent and bring to perfection an economical
process for doing it thoroughly well, sugar-makers and spirit-distillers
will have to be on their guard!
But we are wandering from our subject. If I have allowed myself to
make this digression, however, it is because I am not sorry to accustom
your mind early to the idea of those wonderful transformations which
nature accomplishes, and of which I could give you many other instances.
To return to our flour. As soon as all the starch is gone out of it,
there remains in your hand a whitish, elastic substance, which is also
sticky or _glutinous_, so that it makes a very good glue if you choose;
and hence its name of _gluten_, which is the Latin word for glue.
When dried, this _gluten_ becomes brittle and semi-transparent.
It keeps for an unlimited time in _alcohol_, putrefies very soon
in water exposed to the air, and is easily dissolved in a wash of soda
or potash. Finally 100 ounces of it contain as follows:--
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
---
100
Observe the last material named. It is a new arrival, of which I shall
soon have something to say.
But where am I leading you? you will ask, with all these uninteresting
details about glue.
Wait a little and you shall hear.
You have probably never seen any one bled, which is a pity, as it
happens; for if you had, you might have noticed (provided you had had
the courage to look into the basin), that after a few seconds, the
blood which had been taken away separated itself of its own accord
into two portions; the one a yellowish transparent liquid, the other
an opaque red mass floating on the top, and which is called the
_coagulum_ of the blood or _clot_. This _coagulum_ owes its color to an
infinity of minute red bodies of which we will speak more fully by and
by, and which are retained as if in a net, in the meshes of a peculiar
substance to which I am now going to call your attention.
That substance is whitish, elastic and sticky; and when dried becomes
brittle and semi-transparent. It keeps for an unlimited time in alcohol,
putrefies very soon in water exposed to the air, and is easily dissolved
in a wash of soda or potash. Finally 100 ounces of it contain as
follows:--
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
---
100
This substance is called _fibrine_. It goes to form the fibres of those
muscles which are contained in a half formed state in the blood.
You are laughing by this time I know, and I also know the reason why.
I have told you the same story twice over. You have not forgotten my
wearisome description of _gluten_, and here I am, saying exactly
the same thing of _fibrine_! You conclude I am dreaming, and have
made a mistake!
But no, I am wide awake, I assure you, and mean what I say. And if
these details are the same in the two cases, it is for the simple
reason that the two bodies are one and the same thing; _gluten_ and
_fibrine_ being in reality but one substance, so that were the most
skilful professor to see the two together dried, he would be puzzled to
say which came from the flour, and which from the blood. I mentioned
that our muscles existed in a half-formed state in the blood. Here is
something further. The _fibres_ of muscles exist previously in full
perfection, in the bread we eat; and when you make little round pills of
the crumbs at your side, it is composed of fibres stolen from your
muscles which enable the particles to stick together; and I say _stolen
from your muscles_, because they are the _gluten_ which you ought to
have eaten. I hope the thought of this may cure you of a foolish habit,
which is sometimes far from agreeable to those who sit by you.
This, then, is the first great _aliment of nutrition_, and you
may make yourself perfectly easy about the fate of those who eat bread.
If little girls should now and then have to lunch on dry bread, I do
not see that they are much to be pitied. There is the starch to keep
up their fire, and the gluten for their nourishment, and that is all
they require. The porter above is the only one who finds fault. And
in these days porters have become more difficult to please than the
masters themselves.
Then as to babies who drink nothing but milk, you perhaps wish to know
where they get their share of fibrine.
And I am obliged to own there is none in the milk itself; but, I
daresay, you know curdled milk or _rennet_? The same separation into two
portions has taken place there which occurs in the blood when drawn from
the arm; underneath is a yellowish transparent liquid,--that is the
_whey_; above a white curd of which cheese is made, and which contains a
great part of what would have made butter. By carefully clearing the
curd from all its buttery particles you obtain a kind of white powder
which is the essential principle of cheese, and to which the pretty name
of _casein_ is given because _caseus_ is the Latin for cheese. I shall
not trouble you now with details about _casein_; but there is one thing
you ought to know. A hundred ounces of _casein_ contain as follows:--
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
---
100
Exactly like gluten and fibrine!
Now, then, you can understand that no particular credit is due to the
blood for manufacturing muscles out of the cheese of the milk which
a little baby sucks. He has much less trouble than the manufacturers
at Colmar have in turning their starch into sugar; because in his case
the new substance is not only composed of the same materials as the
old one, but contains them in exactly the same proportion also.
We have a second aliment of nutrition, you see, and I must warn you
that it is not found in milk only. It exists in large quantities in
peas, beans, lentils, and kidney-beans, which are actually full of
cheese, however strange this may seem to you. It would not surprise
you so much, however, if you had been in China and had tasted those
delicious little cheeses which are sold in the streets of Canton. They
cannot be distinguished from our own. Only the Chinese (from whom we
shall learn a great many things when we have beaten them so that they
will conclude to be friends with us)--the Chinese, I say, do without
milk altogether. They stew down peas into a thin pulp. They curdle
this pulp just as we do milk, and in the same way they squeeze the
curd well, salt it, and put it into moulds--just as we do--and out
comes a cheese at last--a real cheese, composed of real _casein_!
Put it into the hands of a chemist, and ask him the component parts
of a hundred grains of it, and he will tell you as follows:--
Ounces.
Carbon 63
Hydrogen 7, etc.