Serge Voronoff sold the early 20th century version of male enhancement – monkey testicles. No, we don't mean the monkey testicles were ground up and put in food, or even swallowed whole. We mean Voronoff stapled them to a person's body.
In the 1920s, a rather open-minded group of men went to Voronoff in hopes of improving their sexual prowess. He hooked them up with a nice pair of executed convict testicles. When defense lawyers got a little better at their jobs, Voronoff had to move on. He changed things up a bit and got monkey testicles.
The surgery not only did not cause Voronoff to go the way of his earliest organ donors, but made him rich. It was so popular that today, there have been speculations that Voronoff's surgery was the origin of the Simian Immunodeficiency Virus making the successful jump to humans and resulting in what we now call HIV. This is relatively unlikely. The SIV virus that mutated most likely came from a subspecies of chimpanzee that Voronoff never used. Even if that were some crossover with subspecies of chimpanzees, it's unlikely that Voronoff's operation ever rendered anyone more likely to have sex.
It did render other people more likely to capitalize off quackery. An American "doctor" who had purchased his degree from a diploma mill (yes, they had them back then) decided to try the same surgery with goat testicles. The doctor, John Brinkley, managed to end the trend of animal testicle implants in the worst way possible — so many of his patients ended up dead that he was exposed as a fraud and jailed, and the surgery was thrust into the spotlight as a dangerous and embarrassing medical scam. Although there have been plenty of subsequent male-enhancement scams, none have gone as far as xenotransplantation.
Top image: Matt Sabbath.