 In the space of six years, McCollum was promoted from instructor to assistant professor, associate professor, and then full professor.He thought that a professor succeeds with his students, "by his ability to make his conversations and lectures more interesting than song, dance, drink and fast driving".Looking at beriberi and the problem of polished rice, Christiaan Eijkman and Gerrit Grijns were trying to find the cause of polyneuritis (influenced by Louis Pasteur.