That the vegetable creation should restore the air which is spoiled by the animal part of it, looks like a rational system, and seems to be of a piece with the rest.

"Letter to Joseph Priestley" in response to Priestley's "experiments on the restoration of air [by plants] made noxious by animals breathing it, or putrefying it..." read in Philosophical Transactions LXII 147-267 of the Royal Society (1772) and quoted in John Towill Rutt, Life and Correspondence of Joseph Priestley... Vol.1 (1831)