Evolution of sleep Sleep is very ancient. In the electroencephalographic sense we share it with all the primates and almost all the other mammals and birds it may extend back as far as the reptiles. There is some evidence that the two types of sleep, dreaming and dreamless, depend on the life-style of the animal, and that predators are statistically much more likely to dream than prey, which are in turn much more likely to experience dreamless sleep. In dream sleep, the animal is powerfully immobilized and remarkably unresponsive to external stimuli. Dreamless sleep is much shallower, and we have all witnessed cats or dogs cocking their ears to a sound when apparently fast asleep. The fact that deep dream sleep is rare among pray today seems clearly to be a product of natural selection, and it makes sense that today, when sleep is highly evolved, the stupid animals are less frequently immobilized by deep sleep than the smart ones. But why should they sleep deeply at all? Why should a state of such deep immobilization ever have evolved? Perhaps one useful hint about the original function of sleep is to be found in the fact that dolphins and whales and aquatic mammals in genera seem to sleep very little. There is, by and large, no place to hide in the ocean. Could it be that, rather than increasing an animal's vulnerability, the University of Florida and Ray Meddis of London University have suggested this to be the case. It is conceivable that animals who are too stupid to be quite on their own initiative are, during periods of high risk, immobilized by the implacable arm of sleep. The point seems particularly clear the young of predatory animals. This is an interesting notion and probably at least partly true
我闭上眼睛，仍能闻到她的气息：粉扑的香味，优雅、安全、坚强，以及一种无条件的爱的气息Hepburn, the Mother I remember whenever she had to go to a dinner or a cocktail party, she would always say, “Oh, if only I could stay home and eat in the kitchen with you.”I remember school days, cramming exams which she probably fretted more than I did. She would test me bee bed and again in the morning, waking up with the sort of sleepy head only adults enjoy.I remember her elation at good grades, her support and positiveness the “not so good ones.”I remember sleepovers on weekends, when we would chat with the lights out. We would talk about feelings and plans and people and things, but in that way that is specific to that darkness, like two souls suspended.I close my eyes and remember, through the nose, her scent powdery, elegant, safe, strong, the scent of unconditional love. I look down and see her delicate hands, their skin so thin I can faintly see their veins, her nails round, soft, and clear. They caressed me, they walked me to school, and I held on to them when I was scared. Oh, how I miss them!
Stopping by Woods on a Snowy Evening---by Robert FrostWhose woods these are I think I know,His house is in the village though.He will not see me stopping here,To watch his woods fill up with snow.My little horse must think it queer,To stop without a farmhouse near,Between the woods and frozen lake,The darkest evening of the year.He gives his harness bells a shake,To ask if there is some mistake.The only other sound's the sweep,Of easy wind and downy flake.The woods are lovely, dark and deep.But I have promises to keep,And miles to go bee I sleep.And miles to go bee I sleep