This Ph.D. dissertation is an intellectual history that traces the development of the investigative pathway carved out by Frank Macfarlane Burnet during the course of his research on bacteriophages. Burnet was a Nobel Prize-winning Australian microbiologist who made seminal contributions to virology and immunology in the mid-20th century. He began his career by studying bacteriophages and made important discoveries in this area between 1924 and 1937. Of particular significance are his studies on phage growth, through which which helped establish the identity of phages as bacterial viruses, a much-debated issue in the scientific community at that time. Also significant is his work on the problem of lysogeny, a matter of considerable controversy among phage biologists, for which Burnet furnished an elegant solution. Using a combination of Burnet's published papers and personal writings, primarily diaries and letters, this dissertation traces the development of his phage work and analyzes its influence on his later research in the disciplines for which he became famous.