Sleep is divided into periods of so-called REM sleep, characterized by rapid eye movements and dreaming, and longer periods of non-REM sleep. 51 kind of sleep is at all well-understood, but REM sleep is 52 to serve some restorative function of the brain. The purpose of non-REM sleep is even more 53 . The new experiments, such as those 54 for the first time at a recent meeting of the Society for Sleep Research in Minneapolis, suggest fascinating explanations 55 of non-REM sleep.
For example, it has long been known that total sleep 56 is 100 percent fatal to rats, yet, 57 examination of the dead bodies, the animals look completely normal. A researcher has now 58 the mystery of why the animals die. The rats 59 bacterial infections of the blood, 60 their immune systemsthe self-protecting mechanism against diseasehad crashed.