“I will now put to you a question. Let us suppose that there are on the hearth some burning brands, but that they are few and small, and you wish to keep the fire as long as possible. Would you let these firebrands burn freely? Would you take the bellows and blow air on them to increase the blaze?” “No,” replied Jules; “that would be just the way to burn up the brands in no time. They must be covered with ashes. If the air comes to them very slowly and only a little at a time, they will burn gradually and the next morning we shall find the coals still alive.” “That is well said, my boy. To keep up a fire for a long time with a given amount of fuel, the draft must be reduced, the access of air must be largely cut off, but not intercepted altogether, because then the fire would be completely extinguished. Therefore the live coals are buried under ashes, and if the fire is in a stove the door of the ash-pit is nearly closed. With plenty of air, combustion is active but of short duration; with only a little air it is feeble, but lasts a long time. “As the maintenance of life is the result of a real combustion, any animal obliged to endure a long fast, or in other words to dispense with the regular renewal of the fuel needed in that combustion, must take into its body as little air as possible. It must reduce the draft of its furnace. This draft is respiration, breathing; and so, in order to go without food for months at a time and to make the small amount of fuel held in reserve in the veins last as long as possible, the animal has but one course to follow: it must breathe as little as it can without depriving itself entirely of air, for that would mean the total extinction of the vital spark, just as the complete cutting off of air from a lighted lamp means the speedy extinction of its flame. There you have the hedgehog’s and the bat’s secret for enduring their long fast through the winter season.