The Marey Pneumograph was a pressure-sensing device and was used to measure respiration. Although it was sensitive it was not terribly accurate but it was the first device able to do what it did. The descriptions of the Marey Pneumograph from the late 1800’s implied that the diaphragm was a disk of thin metal but from this photograph it seems far more likely it was thin rubber or another similar material. The stylus attached to the diaphragm traced a graph of its movement onto a smoked (carbon black) metal drum and is shown here with the diaphragm pressurized. This device was originally called a pneumograph but a later invention of Marey’s, which consisted of an elastic device strapped across the chest that directly measured the expansion and contraction of the thorax with breathing, took that name and this is more correctly known as the Marey Tambour. Photograph is courtesy of Pierre Moutonnet.