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Proponents of animal experimentation (tests, experiments
and "educational" exercises involving harm to animals) claim
that it has played a crucial role in virtually all medical advances.5,6
However, several medical historians argue that key discoveries in
such areas as heart disease, cancer, immunology, anesthesia and psychiatry
were in fact achieved through clinical research, observation of patients
and human autopsy.7-16
Human data has historically been interpreted in light
of laboratory data derived from nonhuman animals. This has resulted
in unfortunate medical consequences. For instance, by 1963 prospective
and retrospective studies of human patients had already shown a strong
correlation between cigarette smoking and lung cancer.17,18 In
contrast, almost all experimental efforts to produce lung cancer in
animals had failed. As a result, Clarence Little, a leading cancer
animal experimenter, wrote: "The failure of many investigators
to induce experimental cancers, except in a handful of cases, during
fifty years of trying, casts serious doubt on the validity of the
cigarette-lung cancer theory."19 Because the human
and animal data failed to agree, this researcher and others distrusted
the more reliable human data. As a result, health warnings were delayed
for years, while thousands of people died of lung cancer.
By the early 1940s, human clinical investigation
strongly indicated that asbestos causes cancer. However, animal studies
repeatedly failed to demonstrate this, and proper workplace precautions
were not instituted in the U.S. until decades later.20
Similarly, human population studies have shown a clear risk from exposure
to low-level ionizing radiation from diagnostic X-rays and nuclear
wastes,21-24 but contradictory animal studies have stalled
proper warnings and regulations.25 Likewise, while the
connection between alcohol consumption and cirrhosis is indisputable
in humans, repeated efforts to produce cirrhosis by excessive alcohol
ingestion have failed in all nonhuman animals except baboons, and
even the baboon data is inconsistent.26
Many other important medical advances have been delayed
because of misleading information derived from animal "models".
The animal model of polio, for example, resulted in a misunderstanding
of the mechanism of infection. Studies on monkeys falsely indicated
that the polio virus was transmitted via a respiratory, rather than
a digestive route.27,28 This erroneous assumption resulted
in misdirected preventive measures and delayed the development of
tissue culture methodologies critical to the discovery of a vaccine.29,30
While monkey cell cultures were later used for vaccine production,
it was research with human cell cultures which first showed that the
polio virus could be cultivated on non-neural tissue.31
Similarly, development of surgery to replace clogged arteries with
the patient's own veins was impeded by dog experiments which falsely
indicated that veins could not be used.32 Likewise, kidney
transplants, quickly rejected in healthy dogs, were accepted for a
much longer time in human patients.33 We now know that
kidney failure suppresses the immune system, which increases tolerance
of foreign tissues.
Nevertheless, society continues to support animal
experimentation, primarily because many people believe that it has
been vital for most medical advances.34 However, few question
whether such research has been necessary or even beneficial to medical
progress. |