The second edition of Physiology of Membrane Disorders represents an extensive revision and a considerable expansion of the first edition . Yet the purpose ofthe second edition is identical to that of its predecessor, namely, to provide a rational analysis of membrane transport processes in individual membranes, cells, tissues, and organs, which in tum serves as a frame of reference for rationalizing disorders in which derangements of membrane transport processes playa cardinal role in the clinical expression of disease. As in the first edition, this book is divided into a number of individual, but closely related, sections. Part V represents a new section where the problem of transport across epithelia is treated in some detail. Finally, Part VI, which analyzes clinical derangements, has been enlarged appreciably. THE EDITORS xi Preface to the First Edition The purpose of this book is to provide the reader with a rational frame of reference for assessing the pa­ thophysiology of those disorders in which derangements of membrane transport processes are a major factor responsible for the clinical manifestations of disease. In the present context, we use the term "membrane transport to refer to those molecular processes whose cardinal function, broadly speaking, is processes" in a catholic sense, the vectorial transfer of molecules-either individually or as ensembles-across biological interfaces, the latter including those interfaces which separate different intracellular compartments, the cellular and extracellular com­ partments, and secreted fluids-such as glomerular filtrate-and extracellular fluids.