This volume, the sixth of the series, represents the natural counterpart of the previous volume, Ultra­ structure of the Digestive Tract. Unlike the latter, however, whose contents fell entirely within the domains of gastroenterology, Ultrastructure of the Extraparietal Glands of the Digestive Tract encom­ passes a few cognate sciences, such as hepatology, pancreatology, and even oral biology, which are usually dealt with separately. This allows, starting from cell biology, embryology, and comparative anatomy, a comprehensive survey of organs that have much in common both structurally and functionally. The chapters of this book have been compiled by well-known experts in the field with the aim not only of reviewing and pointing out the state of the art of the subject covered, but also of giving directions for future work. Furthermore, through the integration of electron microscopy with immunocytochemistry, autoradiography, freeze fracture, maceration, enzymatic digestion, etc., and by providing superb illus­ trative material, the authors substantiate the pivotal role played by modern morphology in under­ standing human physiology and pathology. In fact, it must be stressed, that a consistent part of the tissues studied here are from human origin. We believe that this volume should be read, not only by scientists and teachers active in the field, but also by a larger audience of students and professionals interested in knowing the scientific foundations of biomedicine.