Frederick Banting upon the idea of obtaining insulin from the fetal pancreas. He removed the pancreases from fetal calves at a William Davies slaughterhouse and found the extracts to be just as potent as those extracted from the dog pancreases. By December 1921, he had also succeeded in extracting insulin from the adult pancreas. Pork and beef would remain the primary commercial sources of insulin until they were replaced by genetically-engineered bacteria in the late 20th century. In spring of 1922, Banting established a private practice in Toronto and began to treat diabetic patients. His first American patient was Elizabeth Hughes Gossett,
Frederick Banting eyesight. Banting successfully joined the army in 1915 and spent the summer training before returning to school. His class was fast-tracked to get more doctors into the war and so he graduated in December 1916 and reported for military duty the next day. He was wounded at the Battle of Cambrai in 1918. Despite his injuries, he helped other wounded men for sixteen hours, until another doctor told him to stop. He was awarded the Military Cross in 1919, for heroism. Banting returned to Canada after the war and went to Toronto to complete his surgical training. He studied orthopedic