Lister left Glasgow University in 1869 and was succeeded by George Husband Baird MacLeod. Lister then returned to Edinburgh as successor to Syme as Professor of Surgery at the University of Edinburgh and continued to develop improved methods of antisepsis and asepsis. Amongst those he worked with there, who helped him and his work, was the senior apothecary and later MD, Alexander Gunn. Lister's fame had spread by then, and audiences of 400 often came to hear him lecture. As the germ theory of disease became more understood, it was realised that infection could be better avoided by preventing bacteria from getting into wounds in the first place. This led to the rise of aseptic surgery. On the hundredth anniversary of his death, in 2012, Lister was considered by most in the medical field as "The Father of Modern Surgery".