长难句：For example, it has long been known that total sleep deprivation is 100 percent fatal to rats, yet, upon examination of the dead bodies, the animals look completely normal.
结构剖析：本句由表示转折关系的连词 yet 分为两个部分：第一部分的主干是 it has long been known that...，其中it 是形式主语，that 引导的主语从句作真正的主语；第二部分的主干是 the animals look completely normal，前面的 upon examination of the dead bodies作状语。
