By Michelle Roberts
Health reporter, BBC News
Unethical use of humans as research guinea pigs has long darkened medicine's history.
Most famous are the experiments carried out on large numbers of prisoners by the German Nazi regime in extermination camps during World War II.
Sadly, a new example has recently come to light - the deliberate infection of hundreds of people in Guatemala with sexual diseases like gonorrhoea and syphilis in medical tests that started the year after the war ended.
Evidence of the programme was unearthed by Professor Susan Reverby at Wellesley College, reports the Journal of the American Medical Association.
Its aim was to find a better treatment for venereal diseases.
With troops having returned from the war field incapacitated by venereal diseases rather than battle-wounds, the US government was acutely aware of the dangers of soldiers indulging in sex with prostitutes.
Although they had the drug penicillin to fight syphilis - as well as the calomel-sulpha-thiazole ointment provided in soldier's survival kit to apply "just in case" - experts wanted to look for useful alternatives.
So with a grant from government officials at the National Institute of Health, doctors at a research unit that 10 years later became part of the country's Centers for Disease Control, set out to investigate.
For trial subjects, Dr John Cutler and his team turned to prisoners in Guatemala's national penitentiary.
With the sanction of officials at the Ministry of Justice and the warden of the prison, which housed nearly 1,500 inmates, prostitutes who tested positive for either syphilis or gonorrhoea were allowed to offer their services to the incarcerated men, paid for by US taxpayers through the funds of the Public Health Service.
Disappointed with their early results - not enough of the men seemed to be getting syphilis, even when regularly "serviced" - the researchers began to question the diagnostic tests they were using.
They decided to re-focus their efforts on finding a suitable blood test for syphilis.
For these studies they enlisted the help of 438 children in the national orphanage. Repeated needling of the children revealed that new kinds of blood tests would be necessary to spot true infections and not false ones.
To gather more data, the doctors next studied patients in Guatemala's only mental hospital.
After gaining the cooperation of the institution, in exchange for the promise of much-needed medical supplies as well as cigarettes and a motion picture projector for the inmates, the doctors began their studies.
Rather than use prostitutes to spread the infections, the scientists gathered the purulent discharge from those already infected with syphilis and smeared it on to others using, at best, "uncomfortable and intimate" procedures that lasted for hours.
The patients, who were unaware of what the research for which they had "volunteered" was for, were then treated for the disease. But it is unclear whether everyone was cured.
Keeping track of the hundreds of subjects proved complicated, especially in the asylum when patient's names were forgotten, or the staff called them, for example, "The mute of St Marcos", archived papers of medical officer John Cutler reveal.
By this time, Dr Cultler's supervisor, a physician called RC Arnold, was beginning to question the ethics of the project.
He confided to Cutler: "I am a bit, in fact more than a bit, leery of the experiment with the insane people. They can not give consent, do not know what is going on, and if some goody organization got wind of the work, they would raise a lot of smoke."
Meanwhile, there were debates within the US National Research Council over the ethics of a similar study into gonorrhoea at the Terre Haute prison in Indiana.
Cutler had already begun his own research on gonorrhoea infections in Guatemalan soldiers, again using prostitutes and inoculations with pus from infected boils.
But by 1948, opposition mounted and Cutler was told to finish up his work and return home to the US.
Six decades on, the US is apologising for the acts, saying they run contrary to American values.