le 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 lu