This excellent treatise has undergone a fourth revision. Since the publication of the third edition a voluminous amount of material on alcoholic fermentation has appeared in the literature. The author has endeavored to include only work of fundamental importance, particularly inclining to the practical aspect rather than the theoretical. A noteworthy chapter presents the involved chemistry of fermentation, in which the function of phosphates plays an illuminating part. Significantly the author points out that the fundamental biologic mode of attack on carbohydrates is that revealed by the study of alcoholic fermentation. The subject still remains one of the most interesting in the whole field of biologic chemistry, the limited degree of insight that has already been gained into the marvelous complexity of the cell lending additional zest to the attempt to penetrate the darkness which shrouds the still hidden mysteries. An extensive bibliography has also been prepared.