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
Frederick Banting medicine and, in 1919–1920, was Resident Surgeon at The Hospital for Sick Children. Banting was unable to gain a place on the hospital staff and so he decided to move to London, Ontario to set up a medical practice. From July 1920 to May 1921, he continued his general practice, while teaching orthopedics and anthropology part-time at the University of Western Ontario in London because his medical practice had not been particularly successful. From 1921 to 1922 he lectured in pharmacology at the University of Toronto. He received his M.D. degree in 1922, and was also awarded a gold medal.