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Diorama in the Unit 731 museum in Ping Fan. According to Japanese eyewitnesses, some human subjects that were used in experiments were autopsied while still alive. Probably more than 6,000 prisoners were killed by Unit 731, mostly during experiments. Human experiments were conducted for the development of biological weapons, but also for other purposes such as basic medical research. Photo: Matthias Ziegler

 

3. The secret of all secrets: Human experiments

The Japanese archives on Ping Fan are still not open to the public. But from testimony given by some of the scientists to the US government directly after the war and that made in a Soviet war crimes trial in 1949, some details on the human experiments in Ping Fan are available.

The key purpose of Ping Fan was the development of biological weapons. From the start, this included deadly experiments with humans, to test all kinds of pathogens and any newly developed delivery system. But in addition to the biowarfare experiments, humans were also experimented to death for other purposes, for basic research on new viruses or on frostbite, for example (see "the Songo case" below).

While Unit 731 was extremely careful to keep the human experimentation a total secret in China, many microbiologists in Japan knew about the human experiments. Some results were even published in the scientific literature, where humans used in experiments were referred to "Manchurian monkeys"– a rather simple code, as real animal experiments were labeled with the animal’s proper scientific name.

In Ping Fan, prisoners were used at times for more than one experiment, as long as they survived. Unit 100 in Changshun was scientifically more rigorous and killed all human subjects after an experiment. Today, this is standard procedure for animal tests, because any experiment may have an effect on the test subject and may thus influence the results of a later experiment.

After the experiments, victims were autopsied. According to Japanese eyewitnesses, some of them were cut open alive, to avoid the rapid deterioration of sensitive organs which could have falsified results. The following examples for human tests are from Sheldon Harris’ book Factories of Death:

• Pathogens were injected into victims to determine the minimal dose to cause a disease.
• Bombs filled with plague, anthrax or typhus were exploded near prisoners who were fastened to stakes in the ground.
• Foodstuffs (chocolate, cookies, beer, milk, coffee) were contaminated with pathogens and given to prisoners to determine what types of pathogens in what concentrations could be used for this delivery mechanism.
• A newly developed type of cholera vaccine was tested by vaccinating prisoners with different types of vaccines and infecting them some time later with cholera.
• Prisoners were exposed to extreme cold until their arms or legs were deep frozen, to test different techniques to treat frostbite. Based on experiments in Ping Fan, the Japanese army introduced a new standard method for frostbite-treatment.

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