It turns out there's actually no natural function known in the body for lithium.

事实上我们已知的身体机能,在正常情况下根本不需要锂。

麻省理工公开课 - 化学原理课程节选

Or more carefully, it's way about talking about certain things the body can do when it's functioning properly, when it's well tuned, as we might put it.

或者更谨慎地说是谈论,身体在机能正常的时候,可以进行的一些活动，我们也可以说在音调调好的时候。

耶鲁公开课 - 死亡课程节选