Arallyn Primm writes at Mental Floss:
No one likes to be sick or suffering. Humans have tried to fight against disease and affliction since we could first comprehend “Hey, I ate that root, and now I don’t feel like death!” In the course of trying to find new cures for medical problems, or perceived medical problems, we’ve stumbled more than a few times along the way. Most of the time, treatments simply didn’t work, and were no more harmful than what they were meant to “cure.” Sometimes, though, the medicine was even worse than the condition itself.
1. To cure rabid human or dog bite
To his credit, Pliny the Elder discounted many purely-magical folk cures in his Natural Histories (not to mention writing entire chapters against the eating of infant brains), and was a proponent of several treatments which we now know to have some merit, such as aloe vera to dress burns.
Still, he had more questionable medical advice than credible. His cures for bites from a mad (rabid) human or dog were the same—raw veal or she-goat dung placed over the wound for no less than four days, while the patient takes only lime and hog’s fat internally. If this doesn’t sound so bad, imagine eating nothing but antacids and lard, while having an open wound get more and more infected. If you weren’t dead by the time the rabies actually manifested, you probably wished you were.
2. To cure ganglion cysts
Hit them with a book. A heavy book. The use of Bibles for this purpose gave the colloquial terms for this benign lump on the synovial sheath: Bible cysts, Gideon’s disease, or Bible bumps.
Or don’t. Really, you shouldn’t do this, even if Wikipedia makes it seem like it wouldn’t be a bad idea (why are you getting medical advice from Wikipedia?). While in some circumstances the lump may disappear or be reabsorbed after being thwacked, this method of treatment is second only to puncturing them in an unsterile environment when it comes to causing recurrence and complications. Most ganglion cysts cause no complications on their own, and many will disappear after a few months if left alone.
3. To cure drapetomania or dysaethesia aethiopica
Drapetomania and dysaethesia aethiopica were two different-but-related “conditions” that one Samuel Cartwright saw as prevalent among slaves during the mid-19th century. Drapetomania supposedly caused an “insanity” that drove slaves to run away, while dysaethesia aethiopica caused “partial numbness of the skin,” and “great hebetude” (mental dullness and lethargy).
To cure either condition, you needed only whip the patient. The concept caught on in the South, as it lent an air of science and self-justification to slave owners—Cartwright’s work suggested that the only moral thing to do was to keep slaves in their place for their own good, lest they become afflicted with one of these conditions (he noted how “common” dysaethesia aethiopica was among “Free Negros”). Of course, this quackery was not hard to spot by his contemporaries outside of the South. Frederick Douglass once sarcastically remarked that, since white indentured servants run away, too, “drapetomania” was probably a European condition that had been introduced to Africans by white slave traders.
Read more here.