Frederick Banting, a surgeon with no prior research experience, proposes in 1921 to John Macleod, professor of physiology at the University of Toronto, an experiment to isolate the pancreatic substance that regulates blood sugar — whose absence causes diabetes, then a fatal disease with no effective treatment. Macleod assigns him a laboratory and an assistant, medical student Charles Best. Banting and Best tie off the pancreatic duct of dogs to trigger degeneration of the cells producing digestive enzymes, preserving the cells producing the sought-after hormone, and manage to extract a compound that drastically reduces blood sugar in diabetic dogs. The initial extract proves too impure and toxic for human use; James Collip, a biochemist brought onto the team by Macleod, develops in January 1922 the purification method that allows the first successful injection in a human patient, fourteen-year-old Leonard Thompson, who goes from a near-terminal state to a remarkable recovery within days. The speed between discovery (1921) and clinical availability (1922) is exceptional in the history of medicine, and transforms type 1 diabetes from a certain death sentence into a manageable chronic condition. The University of Toronto sells the insulin patent for a symbolic dollar, an explicit decision to guarantee global access to the treatment without commercial restrictions.