“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?”