If you isolate those immature cells, some of them are less mature than others, some of them have more potential than others.

如果分离这些未成熟细胞,会发现有一些细胞成熟程度更低,它们比其他细胞更具潜能

耶鲁公开课 - 生物医学工程探索课程节选

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