Frederick Banting realized that this procedure would destroy the trypsin-secreting cells but not the insulin. Once the trypsin-secreting cells had died, insulin could be extracted from the islets of Langerhans. Banting discussed this approach with J. J. R. Macleod, Professor of Physiology at the University of Toronto. Macleod provided experimental facilities and the assistance of one of his students, Charles Best. Banting and Best, with the assistance of biochemist James Collip, began the production of insulin by this means. As the experiments proceeded, the required quantities could no longer be obtained by performing surgery on living dogs. In November 1921, Banting hit
William Banting the Public" which contained the particular plan for the diet he followed. It was written as an open letter in the form of a personal testimonial. Banting accounted all of his unsuccessful fasts, diets, spa and exercise regimens in his past. His previously unsuccessful attempts had been on the advice of various medical experts. He then described the dietary change which finally had worked for him, following the advice of another medical expert. "My kind and valued medical adviser is not a doctor for obesity, but stands on the pinnacle of fame in the treatment of another malady, which, as