This book deals with all the aspects related to such an organ. The appendix has been considered a vestigial remnant until the recent discoveries about its active immunologic function. It is particularly important for people living in poor areas of the world to restore the bacterial flora after infections. In addition, the appendix seems to exert an effect in the development of immune-related diseases spreading in developed countries, according to the theory of the safe house. The book is divided in three parts: The first is dedicated to embryology, anatomy and physiology. The second and third ones are dedicated to diagnosis and treatment of inflammatory and neoplastic diseases.