1. It is fairly clear that sleeping period must have some function, and because there is so much of it the function would seem to be important.
很清楚，睡眠必然具有某种作用。睡眠占去那么多时间，所以其作用似乎还是很重要。
It是形式主语，真正的主语是后面that引导的从句。
there is so much of it the function would这里省略了that，是典型的so that结构，引导结果状语从句。
fairly是相当，非常的意思，做副词修饰clear。
2. Speculations about its nature have been going on for literally thousands of years, and one old finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest. "Rest", in terms of muscle relaxation and so on, can be achieved by a brief period lying, or even sitting down.
人们对睡眠作用的种种猜测，确实有数千年之久。一项使人对这个问题感到困惑的奇怪的发现是，睡眠在很大程度似乎并不仅仅是为了使身体得到休息。
have been going是现在完成进行时，从过去到现在一直持续的一个动作。and one old finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest. 这句话有点复杂，其实它的主干非常简单，one old finds is…that makes the problem puzzling是定语从句，修饰finding。 that it looks very much是that引导的表语从句。
in terms of 根据，按照，用……的话，在……方面
He referred to your work in terms of high praise.
他对你的工作大加赞扬。
He thought of everything in terms of money.
他是从钱的角度来看每一件事。
3. The body's tissues are self-repairing and self-restoring to a degree, and function best when more or less continuously active.
人体组织在一定程度上有自我修补和自我恢复的能力，有张有弛地连续活动时，其功能最佳。
more or less 或多或少，大体上，基本上
His explanation was more or less helpful.
他的解释多少有些帮助。
It took more or less a whole day to paint the ceiling.
粉刷天花板用了将近一整天的时间。
4. This might be a plausible hypothesis were it not for two factors.
若不是下面两点，这种假使似乎是有道理的。
were it not for 如果不是
通常情况下遇到这个词组时会用虚拟语气。
5.The implications of all this were that it was not the disturbance of sleep that mattered, but the disturbance of dreaming.
这一切暗示我们：睡眠受到干忧没关系，而做梦受到干忧是有问题的。
not but 不是而是
It was not the picture but the signiture on it that made him interested.
是画上的签名而不是画本身让他感兴趣的。
