The author has been a student of enzymology, first in the departments of anatomy and of internal medicine at the University of Basel and, more recently, in the United States in the departments of cancer research, internal medicine, and pharmacology of the Boston University School of Medicine. He is co-author of publications dealing with hyaluronidase, urease, the effect of benzidine on liver, phosphatase, hydrogenase, and others. Thus he is well qualified to discuss authoritatively a subject which has become increasingly important for the understanding of human physiology and pathology. In the course of the extremely rapid growth of the knowledge in this area, it has become difficult to keep up with the literature even of one's own country, to say nothing of publications in other countries. The purpose of this book is to supply a critical digest of what is known of the role of enzymes in pathogenesis of disease,