“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.”