Book excerpt: "Portraiture as a genre is receiving increased attention at the same time as public curiosity about science is reaching unprecedented levels. Published to coincide with a major exhibition at the National Portrait Gallery, London, and the Sainsbury Centre for Visual Arts, University of East Anglia, Defining Features ... reflects on the nature of the relationships between art, science, medicine and technology by focusing on a selection of portraits that spans more than three centuries."--P. [4] of cover.