What were Priestly's observations in this experiment ?

Explanation

Priestly observed that
a) A candle burning in a closed space of bell jar soon gets extinguished.
b) Similarly, a mouse would soon suffocate in a closed space of the bell jar.
c) But, when he placed a mint plant in the same bell jar, he found that the mouse stayed alive. He also found that the candle when lighted from outside continuously burning in the presence of the mint plant.