This book, the third volume in the series, continues to explore the application of chemistry to our understanding of the functioning of the human in health and disease. It is the objective of the authors to continue to present, in this and subsequent volumes, the biochemical aspects of clinical chemistry, and to indicate how this knowledge applies to the diagnosis of disease and the treatment of the patient. For this purpose, the literature is reviewed carefully and the findings of the different study groups are integrated, to present an overall view of the present status of the various fields. The text is written with the intent to serve in the training of clinical chemists, clinical pathologists, and medical students in clinical biochemistry. It is also intended to serve as a reference text for the practicing physician who desires a more rational approach to the use of the clinical chemistry laboratory, as an aid in understanding (1) the chemical changes in disease and (2) the logical use of the laboratory data in the treatment of the patient. This volume is concerned with the plasma proteins and their significance in normal human metabolism. The immunoglobulins are not included in this study since, along with complement and clotting factors, they form an integrated system concerned with defense against invading organisms. These will be discussed in Volume 4 of this series. A historical introduction (Chapter I) is followed by a general presentation of the composition and properties of proteins (Chapter 2).