Ingenhousz

Dutch Physician 1730-1799

Jan Ingenhousz made major contributions to plant physiology as well as human medicine. He was born in the Netherlands, received a medical degree in 1753, and went on to further study in Leiden, Paris, and Edinburgh, finally aiding in the discovery of a new smallpox inoculation procedure. For a time he lived in England, where he befriended Benjamin Franklin and Joseph Priestley. After his success with the smallpox vaccine, however, Empress Maria Theresa of Austria called Ingenhousz to the Austrian court. There he served as personal physician to the empress for twenty years. He returned to in England in 1778.

Ingenhousz had an early interest in gases, which led to his interest in photosynthesis. The results of his work demonstrated both the disappearance of gas and the production of oxygen during photosynthesis. Ingen-housz disproved the belief that carbon comes from the soil by establishing a relationship between photosynthesis and plant respiration, claiming that the carbon used by plants came from the carbon dioxide in the air. In addition, he showed that only green leaves have the ability to purify the air through photosynthesis.

In 1778 Ingenhousz conducted experiments on plant production of oxygen. He showed that the green leaves of plants must be exposed to substantial daylight for oxygen production to occur. From this result, he was able to counter the arguments and statements of his contemporary chemists regarding the source of oxygen. Ingenhousz began applying many of the techniques pioneered by Priestley to the study of plant respiration. Priestley had designed a mechanism for measuring oxygen called a eudiometer. Nitric oxide was injected into a closed vessel in which there was already water. A reaction would then occur between nitric oxide and the oxygen in water, producing nitrous dioxide, which is soluble in water. Therefore, the amount of oxygen in the water could be measured by watching the water in the vessel rise.

Using this technique, Ingenhousz showed that plants need the presence of light in order to purify air. In the presence of light, he concluded that "all plants possess a power of correcting, in a few hours, foul air, unfit for respiration; but only in clear light, or in the sunshine."

After he had made this conclusion (what we now call carbon fixation), Ingenhousz began thinking about ways in which oxygen might help respiratory patients; he built some equipment for this purpose but never got terribly far.

In addition to his work on carbon fixation, Ingenhousz performed substantial particle research using algae specimens. His research on algae led to his preliminary observations of what would later be called Brownian

Jan Ingenhousz.

physiology the biochemical processes carried out by an organism specimen object or organism under consideration t

hyphae the threadlike body mass of a fungus

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Motion and illustrated that lifeless particles show motion. Notably, Ingen-housz was also the first to use thin glass coverslips for liquid preparations viewed under microscopic lenses. see also Atmosphere and Plants Photosynthesis, Carbon Fixation and; Photosynthesis, Light Reactions and; Physiologist; Physiology; Physiology, History of.

Hanna Rose Shell

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