Comparative Biology
Loses Another Giant: The Passing of Professor Knut Schmidt-Nielsen
(1915-2007)
On January 26, 2007, the comparative physiologist
Knut Schmidt-Nielsen died at his home, surrounded by family, in
Durham, North Carolina at age 91. He represented-indeed stood with
few others as a paradigmatic figure-of what we can recognize as the
classic era in the development, expansion, and recognition of his
field, comparative physiology. His achievements did not go
unrecognized-he received numerous honorary degrees and national
academy memberships and was awarded the first International Prize in
Biology by the Emperor of Japan.
Comparative physiology traces its roots in large
measure to a laboratory in Copenhagen, Denmark, one begun by
Christian Bohr (father of the famous physicist Niels Bohr) and
brought to its peak by August Krogh, Nobel Laureate. The physicists
recognize a so-called Copenhagen School, centering on Niels Bohr;
physiologists might well recognize a parallel-in time as well as
place-a school begun by the earlier Bohr. So well accepted is its
approach to the subject that one easily forgets that before it came
along, "comparative" as a designation referred to work, mainly
anatomical, that inferred ancestry and lineages from studies of
extant organisms. Function was largely ignored; it was a nuisance
that, by driving convergence, complicated analyses. Krogh took
comparative work as a way to recognize the basics of function, a way
to sort out the general from accident and epiphenomenological
adaptation, and he pioneered the use of the diversity of nature in
studies of function. He suggested, as well, that looking at extreme
cases of physiological function and adaptation might have special
value for elucidating functional principles, in revealing nature's
inner secrets-but neither he nor his associates pursued the matter
extensively.
That latter agenda largely remained for his
successors and has continued to this day, initiated in particular by
Knut Schmidt-Nielsen, his close friend and Norwegian compatriot Per
Scholander. Schmidt-Nielsen received his doctorate under Bohr's
sponsorship and spent the war years in occupied Denmark. He came to
the United States in 1946 and spent several years at the invitation
of Lawrence Irving at Swarthmore College, where he began exploring
the water balance of kangaroo rats. He then moved to Stanford
University and the University of Cincinnati; he joined the Zoology
Department at Duke University in 1952, where he remained until well
beyond his formal retirement in 1995. At the time neither that
department nor the university could be considered first-rate; the
subsequent success of the department-and the legacy of physiology
at the Duke Medical School-reflects not just his presence but his
high standards and considerable efforts with respect to all of its
areas and activities.
While his laboratory at Duke remained modest in
both size and expenditures, its output was quite remarkable in both
diversity and significance, a result, in part, of his remarkably
broad curiosity about how animals work. To work done there we can
trace our appreciation of the special value for understanding
temperature regulation and water balance of studies on the physiology
of desert animals, from camels to snails. Counter-current exchange
mechanisms, first recognized by Scholander, took on additional roles
and arrangements-such as the reciprocating flow exchangers
widespread among nasal passages. Salt glands in marine birds and
reptiles put to functional purpose the mock turtle's tears.
Students studied the cost of penguin migrations in Antarctica and
thermogenesis in the heads of marlin and swordfish. The way birds
achieved unidirectional flow through high-efficiency lungs despite
alternating inhalations and exhalations was largely elucidated there.
The use of scaling exponents to deduce function was pressed forward
with Schmidt-Nielsen's written and organizational urgings in the
1970s. (It must be put on record that he was not persuaded by recent
explanations of the significance of the body-mass vs. metabolic rate
scaling exponent of 0.75, recognizing its limitations of both input
data and applicability.) He enjoyed collaborations, even ones of
daunting complexity, and much of his best work took advantage of his
ability not just to inspire, but to organize.
Schmidt-Nielsen's legacy remains as much as
anything in the clarity with which he explained physiological
principles. The increased recognition of the value of a comparative
approach to physiology traces as much to his books and semi-popular
articles as to the direct output of his laboratory and the subsequent
work of his students. One finds it hard to imagine that he long
worried about his mastery of English, but then understands his
intolerance of poor writing by native speakers. He had a special
talent-or, more likely, fastidiousness and tirelessness-for
focusing on central issues and for direct, unambiguous prose. His
first book, Animal Physiology (1960) was a small paperback in
a series designed for first-year biology students. It sold in
enormous number, probably more than any of the other titles,
eventually going into a third edition and multiple translations. It
represents comparative physiology as we now know it when
undergraduates had easy access to nothing else of the sort. Desert
Animals (1964), a larger work, put that area of physiology on the
map. And Scaling (1984) does the same for another
area-defining the issues and catalyzing a renaissance of work that
continues today.
In 1975, Schmidt-Nielsen produced another book
entitled Animal Physiology, this one a full-fledged textbook
for an undergraduate course. Few senior figures in any field invest
valuable mid-career effort in textbook writing, but he had in mind a
particular mission. Now in its fifth edition, the book has
effectively reset the canon for such courses and has become the
standard for college courses around the globe. Previous textbooks
were almost indistinguishable from books on medical or human
physiology. His book and more recent textbooks by others are truly
comparative in the sense that traces to Krogh, as they use diversity
to illuminate principles rather than to infer ancestry or to catalog
nature's range.
He leaves us as well an extraordinarily frank
autobiography, The Camel's Nose (1998). It recounts his
unusual personal history, living in three countries and experiencing
the war. Besides its rich anecdotes about expeditions, people, and
animals, it provides a powerful statement of the utility of studying
animal function in both field and laboratory. But its greatest
interest, and as he told some of us he intended, lies in how he lays
bare his personal problems in order to offset any purely triumphalist
view of a well-rewarded life and to show how one can compartmentalize
one's life to do good science while otherwise experiencing
difficulties.
His books retain their value-any one of them,
from first to last, provides an excellent entry point for a person
intent on entering the field of comparative physiology. And his
influence will long be felt-in particular his stress on the
importance of clear articulation of what science discovers
specifically and of the reality-based world view of the scientist in
general.
Successful scientists fit no simple social
stereotype, ranging from brash extroverts to shy introverts.
Schmidt-Nielsen cannot be readily placed on such a one-dimensional
scale. While certainly shy and quiet, he was at the same time
outspoken and opinionated-but in ways so informed, so subtle, and
so effective that his views usually prevailed. He had an eloquent
style and a soft manner but a firm and well-reasoned position on
issues extending far beyond his area of science. Most often he
prevailed, whether editing a thesis with a student or a paper with a
coauthor or whether calming a university after faculty and president
at Duke did public battle over the location of the Richard Nixon
library. In the department his was a consistent voice for
intellectual quality, whatever the field of an applicant or the
nature of some initiative. Outside the department he was a force for
broad culture, liberalism, and urbanity in a part of the world that
received these only late and grudgingly.
Knut Schmidt-Nielsen was a giant in the field of
physiology. His high standards, compelling intellect and language,
his deep appreciation of the complexity of the natural world and the
process of science inspired those who worked closely with him. His
influence in the field of comparative physiology has been profound,
and he will be deeply missed. Still, his legacy will remain through
the students, post-doctoral fellows, and collaborators who carry the
tradition of his field in a rapidly changing world.
Steven Vogel, Barbara Block, Stephen Wainwright