Once the germ theory had become generally accepted within medicine, the importance of experimental science to the improvement of medical practice could no longer be reasonably doubted. However, clinicians still sought to retain control of how knowledge that had originated in the laboratory was interpreted and applied within practical diagnostics and therapeutics. Thus how practitioners incorporated new scientific knowledge into their medical discourse and practice is a matter for careful empirical inquiry. James Sim Wallace, born in Renfrewshire in 1869 and a graduate in medicine from the University of Glasgow, was a leading figure in British dentistry throughout the first half of the twentieth century. Through an examination of his voluminous writings, we explore how the new ‘chemico-parasitical’ theory of dental caries was accommodated within dentists’ understanding of oral hygiene. The paper also looks at the controversies that surrounded the application of the vitamin theory to the problems of rickets and dental caries, focusing on the contentious interaction between Sim Wallace and his colleagues, on the one hand, and the eminent physiologists May and Edward Mellanby, on the other.
