This volume emphasizes the comparative approach to under- standing
vertebrate renal function. I am convinced that this approach is of
particular value in understanding both the details of renal function at
the cellular and subcellular levels and the renal role in regulating
fluid volumes and solute concentrations. My exposure to this approach
first occurred during a student research experience in the laboratory of
Wilbur H. Sawyer, who also provided an introduction to the works of
Homer W. Smith and August Krogh. The importance of this approach was
reinforced by doctoral and postdoctoral research in the laboratory of
Bodil Schmidt-Nielsen. It has been confirmed through years of personal
experience since then. My research and my understanding of renal
function have been aided through the years by collaboration and
discussion with numerous students and associates. Of particular impor-
tance in developing my views on comparative renal function, and
especially on the relationship of structure to function, has been my
long association with my colleague and friend, Eldon J. Braun. Donald S.
Farner, who suggested the writing of this volume, provided valuable
editorial assistance. Much of my personal research in this area has been
supported over the years by grants from the United States National
Science Foundation and National Institutes of Health. The writing of
this volume was completed while I was in Wiirzburg, Federal Republic of
Germany, supported by a Senior U.S. Scientist Award from the Alexander
von Humboldt Foundation.