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,
William Banting William Banting William Banting ("c." December 1796 – 16 March 1878) was a notable English undertaker. Formerly obese, he is also known for being the first to popularise a weight loss diet based on limiting the intake of carbohydrates, especially those of a starchy or sugary nature. He undertook his dietary changes at the suggestion of Soho Square physician Dr. William Harvey, who in turn had learned of this type of diet, but in the context of diabetes management, from attending lectures in Paris by Claude Bernard. In the early 19th century, the family business of William Banting of St.