This is probably the very first stop-motion animation. Muybridge photographed different poses of a horse skeleton that was imported from New York, early in 1881. It is the first sequence Muybridge shot in a detailed photographic quality.
Eadweard Muybridge by now had two moving pictures to his credit: "Sallie Gardner at a Gallop" and "Athlete Swinging a Pick." In both of those there were living creatures in motion. In "Skeleton of Horse" we know a horse's skeleton didn't start moving unless there was something supernatural at play. Barring ghosts, Muybridge had to manipulate the skeleton and take a series of photos to get the illusion that the skeleton was in motion.
Eadweard Muybridge by now had two moving pictures to his credit: "Sallie Gardner at a Gallop" and "Athlete Swinging a Pick." In both of those there were living creatures in motion. In "Skeleton of Horse" we know a horse's skeleton didn't start moving unless there was something supernatural at play. Barring ghosts, Muybridge had to manipulate the skeleton and take a series of photos to get the illusion that the skeleton was in motion.