And they did that by intentionally infecting calves, by harvesting their skin when they were at a certain point of the disease, and by isolating the virus from the skin of the calves.

他们有意感染很多小牛,当小牛疾病发展到一定程度,就收割牛皮,然后把病毒从牛皮里分离出来

耶鲁公开课 - 生物医学工程探索课程节选

The reason for that is, if you are just engaged in a single crop farming, well you plant it, you take care of it, and then when the times comes you reap it.

其中的原因是,如果只是种庄稼,你先播种,接着你好生照料它们,然后成熟时收割它们

耶鲁公开课 - 古希腊历史简介课程节选