Soil was being eroded and wasted along the Eastern seaboard, and they were using up the great soils of the Mississippi Valley and over time that slave system just somehow wasn't going to work out.

东部沿海地区的土地因被侵蚀而荒废掉,密西西比河谷地区的土地资源即将被耗尽,但就在这种情况下,奴隶制依然能维持南方的经济

耶鲁公开课 - 美国内战与重建课程节选

Or you get a cold, the cold virus takes hold, the viruses start replicating inside of you and it takes some time for immune system to gear up to eliminate it, so we're used to thinking about responses that take some time.

或者你得了感冒,感冒病毒扎根在你的身体中,病毒开始在你体内复制,免疫系统需要一定时间做好准备去消灭它,所以我们曾认为免疫反应需要一定时间

耶鲁公开课 - 生物医学工程探索课程节选