This article examines the role of animation in early instructional medical films through close analysis of the films produced by the collaboration between the American College of Surgeons (ACS) and Eastman Kodak in the late 1920s. The ACS placed medical motion pictures at the center of surgical training and thus established moving images as fundamental to the practice of medicine. These films made extensive use of animation to present surgical sequences that were otherwise impossible to capture on film. By adopting the motion picture as an educational tool, the physician–filmmakers actively constructed medical reality through representations that depended on artifice to convey objective scientific truths. ‘Actual photography’ and animation were blended to visualize the invisible and simplify explanations by reducing the information contained in the visual image. The films simultaneously demonstrate how the motion picture camera served as a tool for medical documentation, training both their objects (the patients) and their subjects (the doctors) in the process.