Ingenhousz, Jan (1730–1799)

Dutch physician and plant physiologist who established in 1779 that in sunlight plants absorb carbon dioxide and give off oxygen. He found that plants, like animals, respire all the time and that respiration occurs in all the parts of plants.

Ingenhousz was born in Breda and studied at Louvain and Leiden and abroad at Paris and Edinburgh, after which he set up a private medical practice in Breda. In 1765, he left for England, going to work at the Foundling Hospital, London, where he successfully inoculated patients against smallpox (using the hazardous live virus). In 1768 he was sent to the Austrian court by George III, to inoculate the royal family, and became court physician there 1772–79. He then returned to England.

Apart from studying plants, Ingenhousz developed in 1776 an improved apparatus for generating large amounts of electricity; he also invented a hydrogen-fuelled lighter to replace the tinderbox, and investigated the use of an air and ether vapour mixture as a propellant for an electrically fired pistol.

Ingenhousz's work Experiments On Vegetables, Discovering their Great Power of Purifying the Common Air in Sunshine, and of Injuring it in the Shade or at Night 1779 laid the foundations for the study of photosynthesis.