" In the case of bloodletting, the first comparative experiment was published in 1836 by the French doctor Pierre Louis, who had treated some pneumonia sufferers by immediately relieving them of a few pints of blood and others by holding off on the leeches for a few days. In the first group, 44% died; in the second, 25%.8 In essence, Dr. Louis had carried out the first-ever clinical trials, and bloodletting came out looking pretty dicey. "

― Rutger Bregman , Utopia for Realists: How We Can Build the Ideal World