The Dercum-Muybridge Collaboration and the Study of Pathologic Gaits Using Sequential Photography.

In the late 1870s and 1880s, prior to the development of movie cameras or projectors, English-American photographer Eadweard Muybridge (1830-1904) photographed sequential images of people and animals in motion, using arrays of sequentially triggered single-image cameras. In 1885, Philadelphia neurologist Francis Dercum (1856-1931) collaborated with Muybridge at the University of Pennsylvania to photograph sequential images of patients with various neurological disorders involving abnormal movements, and particularly various gait disorders, including both the sensory ataxic gait of tabes dorsalis and various spastic gaits. Dercum used tracings of sequential photographic images to plot trajectories of limbs as a way to characterize and distinguish pathologic gaits. The Dercum-Muybridge collaboration produced the first motion-picture sequences of neurological gait disorders ever filmed. These sequences and the trajectory-based studies that derived from them were a milestone in studies of pathologic gaits.