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36th APS President (1963-1964)
Hermann Rahn
(1912-1990)
When APS celebrated its seventy-fifth anniversary at the fall meeting in
Coral Gables in August 1963, Hermann Rahn presided over the session. He
first introduced his friend and colleague, Wallace O. Fenn, nineteenth
president of APS (1946-48), who reviewed the most recent twenty- five years
of the Society's history. Rahn then called on former presidents to speak
briefly on topics of historical, contemporary and prospective interest to
members of the Society and their guests. He began as follows:
"Our Presidents do not wear uniforms and medals and ribbons, but they
wear a halo which is not easily recognized by outsiders. It shines with a
soft blue light which can be seen only by those "in the know."
The twelve talks that constituted this program were subsequently
published in volumes 6 and 7 of The Physiologist.
Hermann Rahn was born in East Lansing, Michigan, but from his graduation
from high school in Ithaca, New York, in 1929, his professional life has
been in general identified with central New York State. He received his A.B.
degree from Cornell University in 1933 and his Ph.D. degree from the
University of Rochester in 1938; he joined the staff of the Department of
Physiology at the University of Rochester School of Medicine and Dentistry
in 1941 and eventually became vice-chairman of that department. In 1956 he
moved west only a few miles to become professor and chairman of the
Department of Physiology at the University of Buffalo (since 1962, the State
University of New York at Buffalo). In 1973 he was honored by appointment as
Distinguished Professor of Physiology.
Rahn has not always been found "at home," however. He has been a visiting
professor at San Marcos University, Lima, Peru (1955); at Dartmouth Medical
School (1962); at the Laboratoire de Physiologie Respiratoire, Centre
Nationale Recherche Scientifique, Strasbourg, France (1971); and at
Max-Planck Institut fur experimentalle Medizin, Gottingen, West Germany
(1977). He has received the honorary degrees of Docteur (H.C.), University
of Paris (1964); LL.D., Yonsei University, Seoul, Korea (1965); D.Sc.
(Hon.), University of Rochester (1973); Titulo de Profesor Honorario,
Universidad Peruana, Lima, Peru (1980); and Doctor Medicinae honoris causa,
Universitat Bern, Switzerland (1981). He was elected to honorary membership
in the Harvey Society of New York in 1960, the American Academy of Arts and
Sciences [AAAS (Boston)] in 1966, the National Academy of Sciences (NAS) in
1968, and the Institute of Medicine of the NAS in 1971. In 1976 he received
a Senior U.S. Scientist Award of the Alexander von Humboldt Foundation.
Beginning with his first appointment to the Editorial Board of the
Society's journals in 1953, Rahn has served APS in many different
capacities. Among other appointments he has been a member of the Board of
Publication Trustees (1959-61) and the Editorial Board for the Handbook
of Physiology (1958-66). With Wallace Fenn, he edited the respiration
section of the Handbook of Physiology. He was a member and/or
chairman of the Education Committee (1958-61), the Perkins Memorial Fund
Committee (1968-80), the Daggs Award Committee (1980-83), and the Honorary
Membership Committee (1979-84). Elected to Council in 1960, he was chosen as
president elect two years later and so continued on Council until he
finished his term as past president in 1965. In 1978 he was recipient of the
Society's Ray G. Daggs Award.
Another of Rahn's interests has been the International Union of
Physiological Sciences (IUPS). He has been a member of the Council (1965-74)
and has served as vice-president (1971-74). While serving on the U.S.
Naitonal Committee (1966-74), he was a member of the Organizing Committee
for the XXIV IUPS Congress (1968) in Washington, D.C. (1965-68). As a member
of this committee he was given the responsibility of organizing the
satellite symposia. This was the first time these symposia were officially
recognized as part of the IUPS Congress. He served as chairman of the
Satellite Symposium Committee for six years. There is no doubt that these
symposia have contributed greatly to the viability of our IUPS Congresses
and to the advancement of physiology as a science.
Rahn's graduate study and first three postdoctoral years are marked by a
series of sixteen papers on the endocrinology of the avian pituitary gland
and the biology of rattlesnakes the latter a subject of interest during the
two years he was an instructor at the University of Wyoming at Laramie. When
Wallace Fenn invited him back to Rochester, endocrinology lost a promising
young investigator. With Fenn and Arthur Otis he began the research on
respiration and pulmonary ventilation for which these three men and their
associates have become so well known. By 1955 Rahn and Fenn had arrived at
their concept, A Graphical Analysis of the Respiratory Gas Exchange: the
O2-CO2 Diagram, published by APS (3). Here the
partial pressure of CO2 is plotted against partial pressure of O2.
The graph can represent the composition of any gas mixture of physiological
significance, as well as any combination of CO2 and O2
tensions in blood, plasma, lymph, or other body fluids.
Asked to describe his training in science and his experience in the
laboratory, Rahn responded as follows:
"Throughout my career it has been my special privilege to be associated
with mentors and peers of unusual talents and imagination in exploring
uncharted areas. It started in 1941 with Wallace Fenn and Arthur Otis in
Rochester where we described the first modern version of the pressure-
volume diagram of the chest (1) in support of our fighter pilots equipped
with positive-pressure breathing masks. These adventures in our primitive,
home-made high-altitude chamber eventually led Fenn and me to publish A
Graphical Analysis of the Respiratory Gas Exchange: the O2-CO2
Diagram (3). The O2- CO2 diagram was the
centerpiece of this book, equivalent to a map on which few roads had been
charted, and only one's imagination limited the future paths that would
later be explored and charted on this diagram in the area of high-altitude
physiology, deep and shallow diving (with Lanphier and Hone), gas bubble
resorption (with H. Van Liew), space travel (with L. E. Farhi), and
artificial and insect gills (with C. V. Paganelli)."
"The O2-CO2 diagram also provided a map charting
the alveolar gas concentration as determined by different
ventilation-perfusion ratios (2) and, with L. E. Farhi, predicting the
alveolar-arterial O2 differences as a consequence of a
logarithmic distribution of ventilation-perfusion ratios in the lung (4).
During the late years in Rochester and early years in Buffalo I had the good
fortune to work with P. Dejours, P. Sadoul, J. Knowles, T. Finley, J. Piiper,
P. Haab, T. Velasquez, C. Lenfant, E. Agostoni, L. E. Farhi, J. West, and P.
Cerretelli, while continuing to chart the various consequences of
ventilation-perfusion distribution on the O2-CO2
diagram, and to work with a young medical student, F. Klocke, who
demonstarted the existence of a normal arterial-alveolar N2
difference in humans (5)."
"When gas exchange limitations of water breathers were mapped for the
first time on the O2-CO2 diagram (6), it showed why
their CO2 partial pressure would not exceed 5 Torr. This opened
up new adventures in unraveling the evolutionary sequences of gas exchange
organs from gills to lungs and, with Kylstra and Lanphier, led to the
demonstration that dogs could successfully breathe water (saturated with O2
at 5 atm) and fully recover. It led also, with B. Howell, to the curious
observations that at various body temperatures lower vertebrates do not
regulate their acid-base balance to maintain a constant pH but rather a
constant relative alkalinity or OH-/H+ ratio (7, 8).
The explanation was later provided by R. B. Reeves who showed that all
vertebrates, including humans, do not regulate acid-base balance to preserve
a constant pH, but rather to regulate a constant protein net charge through
the properties of a special protein buffer, imidazole groups of histidine."
"With O. D. Wangensteen it was demonstrated that gas exchange of the
hen's egg is limited to diffusive transport. In more recent years, with C.
V. Paganelli and A. Ar, we have charted this gas exchange on the O2-CO2
diagram (9, 10) and gained new insights in the limitations of gas transfer
operating under Fick's law and the importance and limitations set by
diffusion coefficients. In the egg, O2 and CO2
concentrations are determined by diffusion-perfusion ratios instead of
ventilation-perfusion ratios, and this may eventually serve as a model for
the gas transfer processes at the alveolar gas-capillary interface of the
lung.
"Much of this work was carried out under unusual circumstances, which in
themselves provided new adventures for me. It started out in the
high-altitude chamber at Rochester and led to high- altitude expeditions in
the Rocky Mountains with A. Otis, S. M. Tenney, R. S. Stroud, and H. Bahnson,
and in Peru with T. Velasquez and A. Hurtado. At Buffalo these carried me
into the high-pressure chambers with E. Lanphier and to the diving Ama of
Korea with S. K. Hong, and in Japan with T. Yokoyama. With W. Garey I went
to the Amazon to study acid-base balance in the electric eel, and during the
last decade, with C. V. Paganelli and many others, I have explored strange
islands in Alaska, Mexico, the Marshall and Midway Islands of the Pacific,
and Spitsbergen in the high Arctic to study diffusive gas transport in eggs
of various native birds."
The names of many of Rahn's associates and disciples can be found in his
complete bibliography. Something of the range and variety of his
investigations, however, is evident from the account given above. Rah's
friends know that it is both high professional competence and unusual
breadth of interest that intensify the "soft blue light' of his halo.
Selected Publications
1. Rahn, H., A. B. Otis, L. E. Chadwick, and W. O. Fenn. The
pressure-volume diagram of the thorax and lung. Am. J. Physiol. 146:
161-178, 1946.
2. Rahn, H. A concept of mean alveolar air and the ventilation-blood flow
relationships during pulmonary gas exchange. Am. J. Physiol. 158:
21-30, 1949.
3. Rahn, H., and W. O. Fenn. A Graphical Analysis of the Respiratory
Gas Exchange: the O2-CO2 Diagram. Washington, DC:
Am. Physiol. Soc., 1955.
4. Farhi, L. E., and H. Rahn. A theoretical analysis of the
alveolar-arterial O2 difference with special reference to the
distribution effect. J. Appl. Physiol. 7: 699-703, 1955.
5. Klocke, F. J., and H. Rahn. The arterial-alveolar inert gas ("N2")
difference in normal and emphysematous subjects, as indicated by the
analysis of urine. J. Clin. Invest. 40: 286-294, 1961.
6. Rahn, H. Aquatic gas exchange: theory. Respir. Physiol. 1:
1-12, 1966.
7. Rahn, H. Gas transport from the external environment to the cell. In:
Development of the Lung, edited by A. V. S. de Reuck and R. Porter.
London: Churchill, 1966, p. 3-23.
8. Howell, B. J., F. W. Baumgardner, K. Bondi, and H. Rahn. Acid-base
balance in cold-blooded vertebrates as a function of body temperature.
Am. J. Physiol. 218: 600-606, 1970.
9. Rahn, H., and O. Prakash (Editors). Acid-Base Regulation and Body
Temperature. Dordrecht, Holland: Martinus Nijhoff, 1985.
10. Rahn, H., and C. V. Paganelli. Transport by gas-phase diffusion:
lessons learned from the hen's egg. Clin. Physiol. Oxf. 5 (Suppl)
3: 1-7, 1985.
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