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of the apparatus of science,” even referred to as “test tubes with
tails.”^25 The rodents used in research become something other than
animals, for they “have no counterparts in nature.”^26
A second, closely related trend involves assumptions about the
generalizability of animal models to human diseases and condi-
tions. Scientists use millions of animals, particularly mice, because
they believe they can extrapolate the results to human beings.
Although some researchers conduct studies on animals to under-
stand clinical conditions that affect animals, most scientists do
not study mice to learn about rodents but to generalize their fi nd-
ings to human problems. The vast majority of research involves
the assumption that the knowledge gained can benefi t humans.
Because of the moral problems inherent in using human subjects
for invasive, harmful research, scientists cannot experiment directly
on people. Moreover, most researchers consider studies conducted
on humans “scientifi cally second-rate.”^27 The inability to control for
different lifestyles, environments, and histories introduces numer-
ous confounding factors into any clinical study using human sub-
jects. Researchers assume that the causal mechanisms at work in
disease and the treatment response are analogous in animals and
humans.^28 In addition, because researchers can stabilize genetic
background and living conditions among animal subjects, studies
using animal subjects are, at least in theory, more likely to produce
reliable data. Finally, because the subjects are not humans, their use
raises no strong moral objections. In biomedical and ethical terms,
then, the mouse “stands in” for a human being. To be sure, few if
any researchers believe that mice and humans are identical organ-
isms. However, they do not see the differences between species “as
undermining the legitimacy of animal experimentation,” and they
believe that they accommodate differences by adjusting for scale.^29
Belief in the generalizability of animal models to human conditions
is part of the “institutional thinking” surrounding scientifi c knowl-
edge. The training of researchers incorporates the use of animal
models early. Along with understanding how to use machines and
instruments and how to write a scientifi c paper, knowing how to
use animal models constitutes the skill set necessary for “doing”