ixtures, leeches, blisters, lancets, and
things of that sort."

"Indeed? Well, then, my heart-burn, I suppose, depends upon bad management
of my fire?" surmised Mr. Bagges.

"I should say that was more than probable, uncle. Well, now, I think you
see that animal heat can be accounted for, in very great part at least, by
the combustion of the body. And then there are several facts that--as I
remember Shakspeare says--

" 'Help to thicken other proofs,
That do demonstrate thinly."

"Birds that breathe a great deal are very hot creatures; snakes and
lizards, and frogs and fishes, that breathe but little, are so cold that
they are called cold-blooded animals. Bears and dormice, that sleep all
the winter, are cold during their sleep, while their breathing and
circulation almost entirely stop. We increase our heat by walking fast,
running, jumping, or working hard; which sets us breathing faster, and
then we get warmer. By these means, we blow up our own fire, if we have no
other, to warm ourselves on a cold day. And how is it that we don't go on
continually getting hotter and hotter?"

"Ah!" exclaimed Mr. Bagges, "I suppose that is one of Nature's mysteries."

"Why, what happens, uncle, when we take violent exercise? We break out
into a perspiration; as you complain you always do, if you only run a few
yards. Perspiration is mostly water, and the extra heat of the body goes
into the water, and flies away with it in steam. Just for the same reason,
you can't boil water so as to make it hotter than two hundred and twelve
degrees; because all the heat that passes into it beyond that, unites with
some of it and becomes steam, and so escapes. Hot weather causes you to
perspire even when you sit still; and so your heat is cooled in summer. If
you were to heat a man in an oven, the heat of his body generally wouldn't
increase very much till he became exhausted and died. Stories are told of
mountebanks sitting in ovens, and meat being cooked by the side of them.
Philosophers have done much the same thing--Dr. Fordyce and others, who
found they could bear a heat of two hundred and sixty degrees.
Perspiration is our animal fire-escape. Heat goes out from the lungs, as
well as the skin, in water; so the lungs are concerned in cooling us as
well as heating us, like a sort of regulating furnace. Ah, uncle, the body
is a wonderful factory, and I wish I were man enough to take you over it.
I have only tried to show you