Originally published in 1901. PREFACE: The object of this work is twofold. In the first place, I have made an attempt to formulate a comprehensive conception of the notion "ferment" on a dynamic basis, and starting from this standpoint to regard the "Theory of Ferments" as a theoretically closed field of discussion. In this conception I have treated the enzymes and organised ferments as a connected whole. In the second place, I have endeavoured to deal as completely as possible with the material to be found in publications on this subject...... Many of the earliest books, particularly those dating back to the 1900"s and before, are now extremely scarce and increasingly expensive. We are republishing these classic works in affordable, high quality, modern editions, using the original text and artwork.