After the pioneering studies by Ussing and co-workers, studies of epithelial Nael transport have come a long way. The first phase of the phenomenological description of the cell as a black box has been follow ed by studies of cellular mechanisms, the interplay of the different trans port components, and the mechanisms of regulation. A broad spectrum of methods has been applied to many epithelia in a variety of species. For the individual epithelia transport schemes have been proposed, and, at this point I think it is appropriate to take a pause and search for elements common to several epithelia. This aspect triggered the publica tion of this book, and in fact the various chapters emphasize that the funetional eomponents, expressed in the various epithelia, are not in finite in number, but they occur in epithelia which are separated in evolu tion by several hundred million years. The authors come both from the field of veterinary and human physiology as weIl as from biology. In my opinion, the close contacts and eollaborations between physiologists and biologists have been essential for the progress in this field. I wish to thank all authors for their con tributions, and I hope that the reader will appreciate this collection of up to date reviews on epithelia in nonvertebrates and vertebrates."

Biological cell membranes regulate the transfer of matter and informa tion between the intracellular and extracellular compartments as basic survival and maintenance functions for an organism: This volume contains a series of reviews that are concerned with how biological plasma membranes regulate the transport of chloride between the intracellular and extracellular compartments of a cell. This book is also an attempt to analyze the molecular basis for the movement of chloride across a cell membrane. This volume is devoted to a diversity of electrogenic chloride transport mechanisms in representative cell membranes of all living things. The first section of the book (Chaps. 1-4) focuses on mech anisms of primary active chloride transport (i.e. photon or A TP-driven), while the second section (Chaps. 5-6) centers on secondary active chloride transporters (symport and antiport) in both plant and animal plasma membranes. The last section, which comprises seven chapters (Chaps. 7-13), deals with chloride channels in cell membranes of prokaryocytes and eukaryocytes of most every phylum. It is hoped that with this particular ordering the reader can glean a telescopic view of the evolutionary history of the various electrogenic chloride transporters."