 She then went on to earn her Doctor of Philosophy in 1947 for a thesis on the chemical synthesis of penicillin – the supply of penicillin to stop wound infection was of high priority, as she did her research during World War II.Muir, a "fiery redhead", never married.The year after she earned her PhD, she worked as a research fellow at the Sir William Dunn School of Pathology at the University of Oxford.