历年考研英语真题mp3之完形填空(1995)

1995
Sleep is divided into periods of so-called REM sleep,
characterized by rapid eye movements and dreaming,
and longer periods of non-REM sleep.
(1)Neither kind of sleep is at all well-understood,
but REM sleep is (2) assumed to serve some restorative function of the brain.
The purpose of non-REM sleep is even more (3) mysterious.
The new experiments,
such as those (4) described for the first time at a recent meeting of the Society for Sleep Research in Minneapolis,
suggest fascinating explanations (5) for the purpose of non-REM sleep.
For example, it has long been known that total sleep (6) deprivation is 100 percent fatal to rats,
yet,(7) upon examination of the dead bodies,
the animals look completely normal.
A researcher has now (8) cast light on the mystery of why the aninlals die.
The rats (9)develop bacterial infections of the blood,
(10)as if their immune systems--
the self-protecting mechanism against disease--had crashed.