Biographical materials, Keilin's address books, personally compiled bibliographies, a collection of Keilin's working notebooks, records and documents pertaining to Keilin's study and work in Cambridge, materials related to publications and conference attendance, correspondence, drawings of parasitological subjects and some of Keilin's colleagues, and some biographical and scientific material relating to Keilin's colleagues, Dr. C.A. MacMunn, Sir Ronald Ross, and Professor G.H.F. Nuttall. The collection includes material belonging or relating to other scientists, for example Dr. C.A. MacMunn, an early and neglected precursor of Keilin's work on cytochrome; there are also correspondence and drawings of Sir Ronald Ross and Professor G.H.F. Nuttall, Keilin's predecessor as Quick Professor of Biology and Director of the Molteno Institute, Cambridge University (Items 223 - 228).