例226　Human beings have agreed, in the course of centuries of mutual dependency, to let the various noises that they can produce with their lungs, throats, tongues, teeth, and lips systematically stand for certain happenings in their nervous systems.

【结构分析】句子的主语是Human beings，动词是have agreed，动词和宾语之间增加了插入语，也就是in the course of centuries of mutual dependency，后面是不定式to let，宾语是the various noises，后面加上定语从句that they can produce with their lungs, throats, tongues, teeth, and lips，再加上宾语补足语stand for certain happenings in their nervous systems，是个let sth do这样一个结构。

【亮点回放】此句话的亮点在于插入语的成功使用，而且里面还有很复杂的定语从句。

【核心词汇】

mutual dependency　相互依赖

systematically　系统地

stand for　代表

certain happenings　某些状况

nervous systems　神经系统

【参考译文】人类在相互依赖生存的几个世纪中慢慢形成一致观点，也就是他们可以用肺部，嗓子，舌头，牙齿，嘴唇所产生的声音来代表神经系统中发生一些情形。