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,
Highest and best use functional obsolescence. Further, there are three potential actions that can be undertaken regarding the existing improvements: Retention of the existing improvements, modification of the improvements or the development scheme of the site, or demolition and removal of the improvements. For example, house A in an area zoned for residential use may have a highest and best use as vacant and a highest and best use as improved that are both residential. A similar house B in a commercially zoned area may have a "highest and best use as vacant" as development to a commercial development, and the "highest and best