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 Since their use predates these regulations, they are "grandfathered in". However, some such uses may not be reproduced if the legally nonconforming improvement is destroyed or damaged beyond a certain point. "Legally permissible" can be a tricky conceptual test, because even uses that are currently not permitted may be considered. This happens when there is a reasonable prospect (at least 50%) that the regulation, zoning, deed restriction, etc. can be changed to permit the proposed use. Any potential use must be physically possible given the size, shape, topography, and other characteristics of the site. For example, a single story warehouse