"Marey became interested in movement at an early stage of his career: the movement of blood as it circulated, the movements which controlled the beating of the heart, then those of the muscles and nerves. To improve his studies, he developed more and more precise recording instruments. Once had explained the internal movements of the body, Marey extended his investigations to the motion of the body as a whole: a walking human being, a flying dragonfly, a swimming ray, a falling cat…"
For those outside of Paris, "Movement In Light" is a stunning online exhibit of Marey's work from which the text above was taken. Link (via AEIOU: Excuse my French!)