A cache of documents related to the Tuskegee syphilis study - a 40-year experiment that tracked infected Black men without treating them - has now been digitized for public use, the National Library of Medicine announced.

The documents concern one of medical history's bleakest chapters. In 1932, officials from the U.S. Public Health Service recruited 600 impoverished Black men in Macon County, Ala., promising them years of free medical care, burial insurance and treatment for an ailment known as "bad blood."

The disease actually was syphilis, and 399 of the participants already had the latent form of the sexually transmitted disease, which was not curable at the time. Doctors tracked them for 40 years and even gave them placebo pills, but they did not treat them for syphilis even when penicillin, now considered a front-line treatment, became widely available. Meanwhile, up to 100 died. The program continued nonetheless. None had given informed consent.

Participants and their descendants discovered the experiment's existence only after a whistleblower leak in 1972, leading to public outcry, a presidential apology and legal reform.

The newly digitized collection includes over 3,000 documents, from the study's inception in the 1930s to the work of the panel that investigated its conduct in the 1970s.

In its final report, part of the collection, the panel concluded the study was unjustified, "scientifically unsound" and should have included penicillin treatment once it became available.

Some of the digitized documents were provided by Fisk University, a historically Black liberal arts university in Nashville.

The experiment still casts a shadow on biomedical research and modern-day medical mistrust. One 2017 analysis connected its dramatic public disclosure in the 1970s to a drop in both health-care use and life expectancy for older Black men.

Although the last survivor died in 2004, 10 of their children continue to receive medical and health benefits through a government-funded program, according to the Centers for Disease Control and Prevention's website.

In September, members of the Voices for Our Fathers Legacy Foundation, a nonprofit group organized by descendants of the unwitting study participants, visited the National Institute of Medicine to see some of the documents before the collection was released.

In a news release, the National Library of Medicine says digitizing the documents will "ensure this chapter in history is never repeated and build greater trust in current biomedical research through transparency."

Although treatable, syphilis continues to circulate in the general population. The CDC recorded 176,713 cases of syphilis in 2021 - a 74 percent increase since 2017.

The documents are accessible online at bit.ly/syphilis-study.