Following the end of World War I, Dr. Banting moved to London, Ontario to start a medical practice. While establishing a medical practise, Dr. Banting spent some of his time working as a medical demonstrator in surgery and anatomy at the University of Western Ontario. As well, he volunteered to work with Dr. Miller, Professor of Physiology, conducting neurological experiments. While researching and preparing a medical lecture on the relation of the pancreas to diabetes he found some interesting studies. When finished the lecture Dr. Banting browsed throught the most recent issue of the Surgery, Gynecology and Obstetrics journal. An article by Moses Barron caught his attention. The article pointed out the anaolgy between the degenerative changes which follow the experimental ligation of the pancreatic duct, and the blockade of the duct by gall stones. After reading this article, Dr. Banting could not sleep, he felt there was some vague relationship between the islet cells of the pancreas and clinical diabetes. It was not until 2 am that he was able to crystallize his thoughts into a form that would allow for experimentation. He wrote the following notes that evening.

Ligate pancreatic ducts of dogs. Wait six to eight weeks for degeneration. Remove the residue and extract."

Dr. Banting presented his idea to Professor Miller, where he was directed to Professor J.J.R MacCleod, at the University of Toronto, who was an authority on carbohydrate metabolism. Since diabetes was a condition where the body failed to metabolize the carbohydrate glucose, J.J.R. MacLeod was a logical choice.

Dr. Banting's hypothesis was that there was an internal secretion in the pancreas that was critical for the metabolism of the carbohydrate glucose (glucose represents the fuel that drives almost all celluar processes). He based this thought on the fact that when the pancreas is removed, diabetes developes rapidly along with other current diabetes research.

After he presented his case, Dr. MacLeod asked him what he hoped to accomplish when the best trained physiologists had not succeeded in establishing or proving that there was an internal secretion of the pancreas. Banting persisted with his idea and requested the use of 10 dogs, an assisstant for eight weeks, and facilities for doing blood- and urine-sugar analysis.

Work commenced on May 16, 1921. Banting was given the use of a laboratory for eight-weeks and ten dogs along with two assistants Mr. C. Best, and Mr. C Noble, each to give four-weeks. Mr. Best won the coin toss, at the end of the four-weeks Mr. Noble did not return and Mr. Best remained throughout the entire experimental duration.

The first step in the experiment was to ligate the pancreatic ducts of several dogs, wait for six-weeks during which the pancreas would atrophy or shrink leaving only the islets of langerhans in tact. As well, several dogs were given pancreatotomy to induce diabetes and to familiarize the researchers with blood and urine analysis to characterize the experimental signs of diabetes.

Several weeks later, the pancreas was removed from a dog after the shrinking process had occured. The tissue was placed in a cold salt solution and ground-up (homogenized) with a mortor and pestle. This homogenate was filtered, and injected into a diabetic dog. The blood glucose sugar went from 0.2 to 0.11 in two hours. This indicated that the extract they injected allowed the body to metabolize glucose, to provide energy for cellular functions. The clinical condition of this dog improved remarkably. Hence, the discovery of insulin was born. The extract was then purfied further and tested in a human on January 11, 1922.