Every force, with one exception, can be seen as a force due to direct contact with the body.

除了一个例外,其它所有力必须要和物体有直接接触

耶鲁公开课 - 基础物理课程节选

It has to be complex, because we're asking the immune system to be able to respond to every potential foreign pathogen that we come into contact with.

免疫系统是十分复杂的,因为我们需要免疫系统,能够对我们身体接触到的,任何潜在的外来病原体进行反应

耶鲁公开课 - 生物医学工程探索课程节选