born April 8, 1850, Norfolk, Conn., U.S.
died April 30, 1934, Baltimore, Md.
U.S. pathologist.
He studied pathology in Germany before returning to the U.S. to open the nation's first pathology laboratory, at Bellevue Hospital Medical College in New York City (1879). From 1893 he directed the rise of Johns Hopkins University, where he developed the country's first true university department of pathology. He recruited William Osler and William S. Halsted for the faculty and was the medical school's first dean (1893–98). His curriculum revolutionized U.S. medicine by demanding that students study physical sciences and be actively involved in clinical duties and laboratory work. Welch also demonstrated the effects of diphtheria toxin and discovered bacteria involved in wound fever and gas gangrene.