In 1804, a medical student in Philadelphia drank fresh vomit from a yellow-fever patient to prove a point. He got his MD for it.

His name was Stubbins Ffirth. He was in his third year at the University of Pennsylvania. The city around him had buried thousands of its own citizens in the yellow-fever epidemics of the 1790s. Ffirth noticed that cases always dropped in winter. He concluded the disease could not be contagious. If it were, he reasoned, winter would not save anyone. The cause, he decided, must be the heat, the bad air, the fear. To prove it, he needed evidence. The evidence, conveniently, was in the buckets beside the hospital beds. He started collecting.

On October 4, 1802, he cut a slit in his own arm and rubbed in fresh black vomit from a dying patient. The wound healed in three days. He cut the other arm. He dripped the vomit into his eyes. Nothing happened. He fried three ounces of it in a pan and breathed the steam. He shut himself in a closet with six ounces heating over sand and inhaled for an hour. He took half an ounce mixed with water and swallowed it. Then he took two ounces straight from the bucket. Then he moved on to blood serum. Then saliva. Then sweat. Then bile. Then urine. He smeared them on his skin. He drank them. He never got sick.

He wrote it all up. On June 6, 1804, the University of Pennsylvania awarded him the degree of Doctor of Medicine. Ffirth's conclusion was that yellow fever was not contagious. He was wrong. Yellow fever is carried by the bite of a particular mosquito. His samples had come from late-stage patients whose blood no longer carried the virus. He had been lucky, not right. It took ninety-seven more years, and Walter Reed on a research station outside Havana, to finish the experiment. Ffirth never knew. He died in South Carolina in 1820, still certain.

I do one of these a day. Dead serious. Subscribe.