Hibernation
    Hibernation is more than sleep. It is a very deep sleep. The animal＇s temperature drops to just over zero centigrade, and its heart beats very slowly. People who find hibernating animals asleep often think that they are dead: the body feels very cold, and the creature may breathe only once every five minutes. A hibernating animal cannot feel any pain. You can touch it, or even pull its tail, without causing it to move or wake up. In its hibernating state it can even live in a poisonous atmosphere for a long time without any ill effect.
    Hibernating in this way, the animal can sleep all through the winter. You might wonder how it manages to live without eating for so many months. The answer lies in two facts. The first is that it has stored supplies of fat in its body during the summer and autumn. The second is connected with the main use the body makes or rood——to supply the energy for movement. We have seen that hibernating animal reduces movement to far below the ordinary level. Even the movements or the heart and lungs are greatly reduced. The animal hardly makes any movement, hardly use any energy, and hardly needs any rood.
    Some animals, including some bears only hair hibernate. That is to say, they sleep during the winter, but their sleep is not deep and their body temperature does not drop, as they are warm blooded animals. In the antumn the bear eats and eats and becomes very rat. His hair grows longer. Soon he has a thick covering or rat and fur. In November he rinds a place to lie down and goes to sleep. On warm winter days he may think spring has arrived；