The bear retires to his den in the beginning of winter, loaded with fat, which he has accumulated from the rich, oily mast abounding in the woods in autumn. There he lies for months, snugly coiled and perfectly dormant; the thickness of his shaggy coat, his dry bed of leaves, and well-protected den, effectually guarding him from cold, which in addition to his want of exercise, draw slightly upon respiration to keep up the vital heat. When the stores of carbon and hydrogen contained in the fat are expended, his hunger and cold compel him to leave his winter-quarters, again to wander in pursuit of food. Many of the swallow tribes, in like manner, hybernate in large hollow trees, and for months eke out a torpid, scarcely perceptible existence, independent of food. Activity and full respiration, on the return of spring, demand a support, which is furnished in the myriads of flies they daily consume. The toad and frog have repeatedly been found in a torpid state, imbedded in limestones, sandstones, and the breccias, where they were probably imprisoned for thousands of years without a morsel of food; yet when exposed to the warmth of the vital air and the stimulus of its oxygen, they have manifested all the activity of their species. This they are enabled to sustain only by an enormous consumption of insects. Dr. Playfair states, that in an experiment made by Lord Ducie, 100 sheep were placed in a shed, and ate 20 pounds of Swedes turnips each per day; another 100 were placed in the open air, and ate 25 pounds per day; yet the former, which had one-fifth less food, weighed, after a few weeks, three pounds more per head than the latter. He then fed five sheep in the open air, between the 21st November and 1st December. They consumed 90 pounds of food per day, the temperature being at 44°, and at the end of this time, they weighed two pounds less than when first exposed. Five sheep were then placed under a shed, and allowed to run about in a temperature of 49°. At first they consumed 82 pounds per day; then 70 pounds, and at the end of the time they had gained 23 pounds. Again, five sheep were placed under a shed as before, and not allowed to take any exercise. They ate at first, 64 pounds of food per day, then 58 pounds, and increased in weight 30 pounds. Lastly, five sheep were kept quiet and covered, and in the dark. They ate 35 pounds per day, and increased eight pounds. Mr. Childers states, that 80 Leicester sheep in the open field, consumed 50 baskets of cut turnips per day, besides oil-cake. On putting them in a shed, they were immediately able to consume only 30 baskets, and soon after but 25, being only half the quantity required before, and yet they fattened as rapidly as when eating the largest quantity. The minimum of food, then, required for the support of animals, is attained when closely confined in a warm, dark shelter; and the maximum, when running at large, exposed to all weathers. THE FEEDING OF ANIMALS.