Born in Manchester, England, Harden did his undergraduate work at a local school, Owens College, but went to the University of Erlangen in Germany for graduate studies. After obtaining his Ph.D. there in 1888, he returned home and spent ten years teaching at his alma mater. In 1898, he began studying fermentation simply because he thought it might help him differentiate between several varieties of bacteria. Although his original theory did not work out, Harden gradually became more and more interested in fermentation itself, the process by which a certain few agents seemed able to cause a number of organic compounds first to decompose, then to transform themselves into other compounds altogether.

The most commonly-seen example of the process--and the one that especially intrigued chemists during the mid-to-late 1800s--was alcoholic fermentation, the conversion of glucose and other sugars into alcohol apparently through the action of yeast preparations. For a...