How far would you go to prove a theory? Stubbins Ffirth, a doctor-in-training living in Philadelphia during the early nineteenth century, went further than most. Way further.
Having observed that yellow fever ran riot during the summer, but disappeared during the winter, Ffirth concluded that it was not a contagious disease. Instead, he theorized it was caused by an excess of stimulants such as heat, food, and noise.
To prove his theory, Ffirth set out to demonstrate that no matter how much he exposed himself to yellow fever, he wouldn’t catch it. He started by making small incisions on his arms and pouring “fresh black vomit” obtained from a yellow-fever patient into the cuts. He didn’t get sick.
Next he dribbled some vomit in his eyes. He fried some up on a skillet and inhaled the fumes. He fashioned some into a pill and swallowed it. Finally he took to drinking entire glasses of pure, undiluted black vomit. And still he didn’t get sick.
Ffirth rounded out his experiment by liberally smearing himself with other yellow-fever tainted fluids: blood, saliva, perspiration, and urine. Healthy as ever, he declared his theory proven. Unfortunately, he was wrong. Yellow fever is very contagious, but it requires direct transmission into the blood stream, usually by a mosquito, to cause infection. But considering all Ffirth did to infect himself, it is a bit of a miracle he remained alive.