Marey started by studying blood circulation in the human body. Then he shifted to analyzing heart beats, respiration, muscles (myography), and movement of the body. To aid his studies he developed many instruments for precise measurements. For example, in 1859, in collaboration with the physiologist Auguste Chauveau and the watch manufacturer Breguet, he developed a wearable "Sphygmograph" to measure the pulse. This sphygmograph was an improvement on an earlier and more cumbersome design by the German physiologist Karl von Vierordt. In 1869 Marey constructed a very delicate artificial insect to show how an insect flies and to demonstrate the figure-8 shape it produced during movement of its wings. He fixed a gold foil to an insect wing and shone light on it to study the flapping of the wing. He also used a soot covered glass-fibre introduced along the path of the insect wing to determine if it crossed with the wing in the upper stroke or lower stroke by examining the side on which the soot was cleared. Then he became fascinated by movements of air and started to study bigger flying animals, like birds. He adopted and further developed "animated photography" into a separate field of chronophotography in the 1880s. His revolutionary idea was to record several phases of movement on one photographic surface. In 1890 he published a substantial volume entitled "Le Vol des Oiseaux" ("The Flight of Birds"), richly illustrated with photographs, drawings, and diagrams. He also created stunningly precise sculptures of various flying birds.