Considered by many to be the Greatest American Painter of the 19th century, although recognition didn't come until the latter part of his life and prior to that he was often the subject of controversy, criticism and isolation because of his radical ideas, particularly his insistence on working from nude models.   He spent most of his life in Philadelphia where he was born but did spend a few years training in Europe where he studied in Paris with Gérôme and also learning from the Spanish painters Velázquez and Ribera.   He taught at the Pennysylvania Academy of Fine Arts in 1876 but was forced to resign after permitting a mixed class to draw from a completely nude male model.   Further controversy was to arise following his painting "The Gross Clinic" with it's clinical depiction of surgery.