William Halsted wrote to aging surgeon, Stephen Smith, in 1919, that he remembered the lessons Smith had taught him, "when I walked with you through the wards of Bellevue Hospital." Smith was an early advocate of Joseph Lister's antiseptic method, and because of his public health work, he was also an early advocate of environmental hygiene and microbial control based on the unproved germ theory. While Lister's work at the time emphasized germ-killing around the operative site with carbolic acid (antisepsis), Smith adopted and encouraged surgical practices at Bellevue that would be hallmarks of the germ-preventing (asepsis) surgical approach that fully developed after German bacteriologic discoveries in the mid-1880s, and with which Halsted is historically identified. Some physicians and historians have emphasized temporal and conceptual differences between Lister's antisepsis and German asepsis, but Smith and Halsted's experiences argue that surgical asepsis was the evolutionary outcome of germ theory-based surgical changes that began well before scientific proof arrived.