2000 HSS/PSA Program 1 - History of Science Society

HSS Abstracts
“global laboratory” . Most recently, through the accumulation and application
of traditional knowledge, science is reasserting the oldest image of the Arctic,
that of homeland. Of particular significance is the interaction between these
views of the Arctic environment, and the intellectual and institutional evolution
of Canadian science since the Second World War. These views have influenced,
and have themselves been influenced by, evolving scientific ideas. Views of
the Arctic as, for example, a storehouse of resources, a harsh, demanding
environment, a fragile wilderness, or an international commons, have also
helped to justify increasing funding for northern science, and the creation of
new research agencies. Demands on scientists implied by these institutions,
and by the political context of these institutions—that, for example, they provide
not general theory, but quantitative, testable, specific information about the
Arctic environment—also illustrate how the political and social roles of Arctic
science relate to scientific theory, and to the contribution of science to the
formation of more general ideas about the environment.
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Sabine Brauckmann University of Münster
Chemical Embryology: The Search for the Organizer
Experimental embryologists in the 1930s attempted to solve the crucial issue
of how an embryo develops its specific shapes during ontogenesis. I will focus
on Conrad H. Waddington’s first approach of the “epigenetic landscape” , and
roughly sketch how Waddington, Joseph Needham and Jean Brachet among
others, searched to define the chemical nature of Hans Spemann’s Organizer.
I will briefly describe the transplantation experiments that Spemann and his
co-workers conducted in the 1920s. These showed that a transplanted
blastoporal lip could induce a nearly complete pattern of organ anlage and an
axial system, a chimeric structure composed of both donor and host cells.
Spemann called this the “Organizer Effect” . Hans Correns had correctly
pointed out to Spemann in 1921 that the Organizer might provide for the correct
sequential activation of the genes involved in development, but Spemann was
never to deal with this genetic thread in his research nor terminology.
Waddington’s significant point of departure was to search for the chemical
nature of the Organizer, and to clarify embryonic terminology. Encouraged by
the members of the Club of Theoretical Biology at Cambridge, Waddington
developed a physico-chemical model for sequential morphogenesis during
embryogenesis. With a ball game based on the two-dimensional equipotential
systems of Hans Driesch and a topographic surface pattern as equated by Alfred
Lotka, Waddington simulated embryonic differentiation in a series of steady
states that resulted in the equilibrium of development. He visualised the
developmental system as “canalized” and pictorially represented it by
bifurcations, an epigenetic landscape of hills and valleys, the landscape
(choices) changing as development progressed. Needham summarized their
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