text: Elmer V. McCollum, the Department’s first Professor and Chair, discovered vitamins A, B and D, as well as the importance of trace metals in diets. McCollum was the chair of the department for 27 years, from 1917 until 1944. After stepping down as the Chair of the Department, McCollum went on to help establish the McCollum-Pratt Institute at the Johns Hopkins University Homewood Campus.