"Schwann (1837) the codiscoverer of the yeast cell, showed by experiment that fermentation and putrefaction were of microbial origin. He also disproved spontaneous generation: with sterile flasks and media he demonstrated that it was microorganisms in the air that produced putrefaction or fermentation of substances. Alcohol was produced when yeast was added to a sugar solution. When sterile media were exposed to the air, they decomposed, but if air was sterilized by heat, no decomposition occurred. Schwann reasoned that the air contained living germs that produced the putrefaction because arsenic and mercuric chloride, which were known to kill living things, also prevented putrefaction. These were the same kind of experiments Pasteur was to perform a quarter-century later. Schwann was the originator but Pasteur got the recognition. This is not to belittle Pasteur, whose many achievements earned him his place in history."