17th century illustration showing British physician John Mayow's (1641-1679) experiment on combustion and respiration.The study of combustion (top left) and respiration (middle left) showed that only a fifth of the air was used in these processes. The combustion apparatus focuses sunlight and ignites tinder inside the jar. The change in the amount of air is measured by the rise in the height of water inside the jar, which has its base immersed in a bowl of water. The respiration apparatus contains a mouse on an elastic membrane. The mouse breathed the air and the membrane inflated as the pressure inside the chamber decreased. Lavoisier, a century later, used oxygen to explain the results. Artwork from Mayow's Tractatus quinque (1674).