In and before 1772, Joseph Priestley conducted a series of experiments to determine the effects of gases on plants and animals. He observed that (1) if a candle was lighted in an airtight container, the flame would soon extinguish; (2) a mouse died soon when put in an airtight container in which a candle has burned out or the air inside has been spoiled by mice breathing and dying in it; and (3) the mouse lived if at the same time a live plant is placed inside the airtight container. He demonstrated that putting a sprig of mint in an airtight jar in which a candle had burned out restored the air. After only 10 days, another lighted candle burned again inside. Aside from mint, Joseph Priestley likewise found that the purifying effect of plants on “injured” air also applies to balm, groundsel which has an offensive smell, and spinach