This is a continuation and the completion of the text of a large work on methods of investigating enzymes. The bibliography and index still remain to be published. The contents of the present volume begin with page 2589. The general subject matter includes: Aspartase by Jorma Erkama and A. I. Virtanen, Helsinki. Peroxydase and catalase by Karl Zeile, Göttingen. Hydrogenase by M. Stephenson and D. D. Woods, Cambridge, England. Reducing substances of unknown mechanism: the thiol disulfide system by Theodor Bersin, Marburg, ascorbic acid by Peter Holtz, Rostock, and quinone bodies by F. Lynen, Munich. Assimilation: carbon dioxide by M. Steiner, Göttingen, and Horst Engel, Münster, nitrogen by A. Virtanen and Tauno Laine, Helsinki. Antienzymes by J. B. Sumner, Ithaca, N. Y. Ferment models by Wolfgang Langenbeck, Dresden. The enzymes of the industries: brewing by Hugo Haehn, Berlin; fat by Emil Hoyer, Rostock; malt extract by S. Preiz, Breslau; baking