Gruesome details of American-run venereal disease experiments on Guatemalan prisoners, soldiers and mental patients in the years after World War II were revealed this week during hearings before a White House bioethics panel investigating the study’s sordid history.

From 1946 to 1948, American taxpayers, through the Public Health Service, paid for syphilis-infected Guatemalan prostitutes to have sex with prisoners. When some of the men failed to become infected through sex, the bacteria were poured into scrapes made on the penises or faces, or even injected by spinal puncture.

About 5,500 Guatemalans were enrolled, about 1,300 of whom were deliberately infected with syphilis, gonorrhea or chancroid. At least 83 died, but it was not clear if the experiments killed them. About 700 were treated with antibiotics, records showed; it was not clear if some were never treated.

The stated aim of the study was to see if penicillin could prevent infection after exposure. But the study’s leaders changed explanations several times.