Walden 30

Walden

by Henry David Thoreau

Of course the vital heat is not to be confounded with fire; but so much for analogy. It appears, therefore, from the above list, that the expression, animal life, is nearly synonymous with the expression, animal heat; for while Food may be regarded as the Fuel which keeps up the fire within us -- and Fuel serves only to prepare that Food or to increase the warmth of our bodies by addition from without -- Shelter and Clothing also serve only to retain the heat thus generated and absorbed.