The sixth volume of these collected reviews, which have become almost indispensable to those interested in keeping abreast of recent developments in biochemistry, maintains the high standard of previous years. The present issue is further improved as a reference book by inclusion for the first time of an excellent subject index; the editorial committee indicates that a cumulative index covering the earlier volumes will be published later. This will remedy a really serious deficiency. The subjects covered in the present reviews include permeability, biologic oxidations and reductions, enzymes, microchemistry, chemistry of carbohydrates and glucosides, lipins, steroids, proteins and amino acids, sulfur compounds, nucleic acids, purines and pyrimidines, metabolism of carbohydrates, fats and proteins and amino acids, detoxication mechanisms, hormones, vitamins, nutrition, biochemistry of muscle, metabolism of brain and nerve, biochemistry of fish, chemical embryology, plant pigments, alkaloids, photosynthesis, mineral nutrition and organic acids of plants, biochemistry of bacteria, and immunochemistry.