As I see it, the official function of this simile is to give us a sense of the size of Satan's shield and thereby to give us a sense of the size of Satan himself.

在我看来，这个比喻的正式的作用,是要给我们展现出撒旦的屏障的规模,因此来展现撒旦自身的伟岸。

耶鲁公开课 - 弥尔顿课程节选

Because of that they're barriers, they separate the inside of the cell from the outside of a cell, and only certain kinds of molecules can pass through a cell membrane.

因为它们的屏障作用,将细胞内外区隔开来,只有特定的,某些分子才能穿过细胞膜

耶鲁公开课 - 生物医学工程探索课程节选

We talked about this a little bit in section last week, when you eat vegetables or meat, you're eating a lot of DNA but that doesn't enter the cells of your body because of the barrier properties of cell membranes.

这个我们上周讨论会讲过一些,我们在吃蔬菜或者肉类时,摄入了大量DNA,它们之所以不会进入你的体细胞,就是由于细胞膜的这种屏障作用

耶鲁公开课 - 生物医学工程探索课程节选