When you would take the fluid from the cow, and you would inject it underneath the skin of a person you wanted to protect, then at that site where you injected it, you would get a lesion that looked like a smallpox or cowpox lesion.

当你从奶牛上得到脓液,并把脓液注射到想受到保护的,人的皮肤下面,然后在你注射的地方,你会看到像天花或者牛痘一样的病变

耶鲁公开课 - 生物医学工程探索课程节选