The first edition ofthe Textbook of Medical Physiology was written by Arthur C. Guyton almost 60 years ago. Unlikemost major medical textbooks， which often have 20 or more authors， the first eight editions of the Textbook of Medical Physiology were written entirely by Dr. Guyton， with each new edition arriving on schedule for nearly 40 years. Dr. Guyton had a gift for communicating complex ideas in a clear and interesting manner that made studying physiology fun. He wrote the book to help students learn physiology， not to impress his professional colleagues.
　　I worked closely with Dr. Guyton for almost 30 years and had the prMlege of writing parts of the ninth and tenth editions. After Dr. Guyton's tragic death in an automobile accident in 2003， I assumed responsibility for completing the subsequent editions.
　　For the thirteenth edition of the Textbook of Medical Physiology， I have the same goal as for previous editionsto explain， in language easily understood by students， how the different cells， tissues， and organs of the human body work together to maintain life.
　　This task has been challenging and fun because our rapidly increasing knowledge of physiology continues to unravel new mysteries of body functions. Advances in molecular and cellular physiology have made it possible to explain many physiology principles in the terminology of molecular and physical sciences rather than in merely a series of separate and unexplained biological phenomena.
　　The Textbook of Medical Physiology， however， is not a reference book that attempts to provide a compendium of the most recent advances in physiology. This is a book that continues the tradition of being written for students. It focuses on the basic principles of physiology needed to begin a career in the health care professions， such as medicine， dentistry， and nursing， as well as graduate studies in the biological and health sciences. It should also be useful to physicians and health care professionals who wish to review the basic principles needed for understanding the pathophysiology of human disease.