"That reminds me of the man in love crying,
' Fire! fire! ' and the laxly said, ' Where,
where? " And he called out, 'Here! here! '
with his hand upon his heart. Eh?—but
now I think of it—you said, the other day,
that breathing was a sort of burning. Do
you mean to tell me that I—eh?—have fire,
fire, as the lover said, here, here—in short,
that my chest is a grate or an Arnott's
stove ?"

"Not exactly so, uncle. But I do mean to
tell you that you have a sort of fire burning
partly in your chest; but also, more or less,
throughout your whole body."

"Oh, Henry! " exclaimed Mrs. Wilkinson,
"How can you say such horrid things!"

"Because they 're quite true, mamma—but
you needn't be frightened. The fire of one's
body is not hotter than from ninety degrees
to one hundred and four degrees or so. Still
it is fire, and will burn some things, as you
would find, uncle, if, in using phosphorus, you
were to let a little bit of it get under your
nail."

"I 'll take your word for the fact, my boy,"
said Mr. Bagges. "But, if I have a fire burning
throughout my person—which I was not
aware of, the only inflammation I am ever
troubled with being in the great toe—I say,
if my body is burning continually—how is it
I don't smoke eh ? Come, now!"

"Perhaps you consume your own smoke,"
suggested Mr. Wilkinson, senior, " like every
well-regulated furnace."

"You smoke nothing but your pipe, uncle,
because you burn all your carbon," said Harry.
"But, if your body doesn't smoke, it steams.
Breathe against a looking-glass, or look at
your breath on a cold morning. Observe how
a horse reeks when it perspires. Besides—as
you just now said you recollected my telling
you the other day—you breathe out carbonic
acid, and that, and the steam of the breath
together, are exactly the same things, you
know, that a candle turns into in burning."

"But if I burn like a candle—why don't I
burn out like a candle ? " demanded Mr.
Bagges. " How do you get over that ?"

"Because," replied Harry, " your fuel is
renewed as fast as burnt. So perhaps you
resemble a lamp rather than a candle. A
lamp requires to be fed; so does the body—
as, possibly, uncle, you may be aware."

"Eh ?— well— I have always entertained an
idea of that sort." answered Mr. Bagges,
helping himself to some biscuits. " But the
lamp feeds on train-oil."

"So does the Laplander. And you couldn't
feed the lamp on turtle or mulligatawny, of
course, uncle. But mulligatawny or turtle
can be changed into fat—they are so,
sometimes, I think—when they are eaten in large
quantities, and fat will burn fast enough.
And most of what you eat turns into
something which burns at last, and is consumed
in the fire that warms you all over."

"Wonderful, to be sure," exclaimed Mr.
Bagges. " Well, now, and how does this
extraordinary process take place?"

"First, you know, uncle, your food is
digested—"

"Not always, I am sorry to say, my boy,"
Mr. Bagges observed, " but go on."

"Well; when it is digested, it becomes a
sort of fluid, and mixes gradually with the
blood, and turns into blood, and so goes over
the whole body, to nourish it. Now, if the
body is always being nourished, why doesn't
it keep getting bigger and bigger, like the
ghost in the Castle of Otranto?"

"Eh ? Why, because it loses as well as
gains, I suppose. By perspiration— eh— for
instance ?"

"Yes, and by breathing; in short, by the
burning I mentioned just now. Respiration,
or breathing, uncle, is a perpetual
combustion."

"But if my system," said Mr. Bagges, " is
burning throughout, what keeps up the fire in
my little finger—putting gout out of the
question ?"

"You burn all over, because you breathe
all over, to the very tips of your fingers'
ends," replied Harry.

"Oh, don't talk nonsense to your uncle!"
exclaimed Mrs. Wilkinson.

"It isn't nonsense," said Harry. " The air
that you draw into the lungs goes more or
less over all the body, and penetrates into
every fibre of it, which is breathing. Perhaps
you would like to hear a little more about
the chemistry of breathing, or respiration,
uncle ?"

"I should, certainly."

"Well, then; first you ought to have some
idea of the breathing apparatus. The
laboratory that contains this, is the chest, you
know. The chest, you also know, has in it
the heart and lungs, which, with other things
in it, fill it quite out, so as to leave no hollow
space between themselves and it. The lungs
are a sort of air-sponges, and when you
enlarge your chest to draw breath, they swell
out with it and suck the air in. On the
other hand you narrow your chest and
squeeze the lungs and press the air from them;
—that is breathing out. The lungs are made
up of a lot of little cells. A small pipe—a
little branch of the windpipe—opens into each
cell. Two blood-vessels, a little tiny artery,
and a vein to match, run into it also. The
arteries bring into the little cells dark-
coloured blood, which has been all over the
body. The veins carry out of the little cells
bright scarlet-coloured blood, which is to go
all over the body. So all the blood passes
through the lungs, and in so doing, is changed
from dark to bright scarlet."

"Black blood, didn't you say, in the
arteries, and scarlet in the veins? I thought
it was just the reverse," interrupted Mr.
Bagges.

"So it is," replied Harry, " with all the
other arteries and veins, except those that