Priestley, a British priest and chemist, also made an interesting experiment at 177 1 to verify his theory that there are "good air" and "bad air" in nature. At the same time, Priestley put two mice in two sealed bell jars, one of which contained a vigorous plant. Soon, the mice without plants gradually reduced their activities and died soon; In another bell jar with green plants, the mouse can still carry out normal activities and continue to live for a few days. Priestley also put the burning candle with the vigorous growth of mint, and the candle didn't go out for a long time.

According to these experiments, priestley came to the conclusion that plants can turn bad air into good air, while animals' breathing and candle burning can turn good air into bad air.