This "focal infection therapy" seemed so scientific and promising that Cotton and his assistants yanked more than 11,000 teeth. He also removed those of his wife and children as a precautionary measure. When patients who lost their molars and incisors didn't recover, Cotton saw it as a sign he hadn't gone far enough: He'd remove their spleens, stomachs, and colons, too.

Unfortunately, this was before antibiotics, so many of his patients died on the operating table. Still, Cotton was lauded as a leader in his field by medical journals and his peers at the time. Occasionally allegations would surface that he was abusing his patients, but he always seemed to placate critics. Once, he escaped scorn by replacing all his male nurses with female ones, according to a 1910 New York Times story. "Men are naturally too rough with the patients," the article's author wrote. "[Cotton] believes the presence of women nurses is restful to the diseased mind."

Eventually, Cotton got the sense he was losing his own mind. He removed several of his teeth in an attempt to cure himself and kept on working. Cotton died of a heart attack in 1933.

Cotton's experiments were unethical and awful, but they weren't that illogical if you consider the knowledge that was available at the time. This was before surgeons operated with gloves on, before doctors knew that people shouldn't stand in front of X-ray machines for 45 minutes, and before people knew about blood types or heroin addiction or that eugenics is not a thing.

If you had no idea about neurotransmitters or lobes, it makes a weird sort of sense that micro-infections in the head would be the true cause of schizophrenia. To quote the tagline from my Knick screeners, "Modern medicine had to start somewhere."

Henry Cotton/Wikimedia Commons

We've come a long way, but as a health writer, it's also a reminder of how little we still know about the brain. Certainly, science has progressed to the point where patients aren't subjected to painful and permanent procedures without their consent, and we obviously now know the basic mechanisms behind mental illness. But we still don't know, say, the very best way to prevent schizophrenia or to treat addiction. It was just a few years ago that a major study found that antidepressants are basically useless for mild depression.

To some extent, the brain remains a bit of a black box, as puzzling to modern-day psychiatrists as it was to turn-of-the-century charlatans. The difference is, most doctors today have the humility to admit what they don't know.