Fleming: At this time my assistant upstairs was doing an experiment. He was careless. Some mould drifted in through an open window and landed in my dish.

• 这时我的一个助手正在楼上做实验。他一时大意，没有发觉他正在使用的霉菌从开着的窗户飘了出去，落进了我那只没盖盖子的器皿。