Jan Ingenhousz

Dutch physician and physiologist

• Born: December 8, 1730; Breda, Netherlands
• Died: September 7, 1799; Calne, England

Jan Ingenhousz began his scientific career by traveling throughout Europe administering smallpox inoculations. After settling in England, he performed botanical experiments that demonstrated the process of photosynthesis and respiration in plants, and was an early investigator of what became known as Brownian motion.

Also known as: Jan Ingen Housz; Jan Ingen-Housz

Primary field: Biology

Specialties: Botany; physiology

Early Life

Jan Ingenhousz was born on December 8, 1730, the son of Arnoldus Ingenhousz and Maria Beckers Ingenhousz. His father bought and sold hides for use in leather goods before becoming a successful apothecary—a dispenser of curative advice and pharmaceutical substances—and the later occupation may have inspired his son to train for the medical profession.

Ingenhousz, who had a facility for languages, was educated at the local Latin School. At the age of sixteen, he entered the Catholic University of Leuven in Belgium. Founded in 1425, it was the oldest institution of higher learning in the country before reorganizing in 1968. Ingenhousz earned a medical degree in 1753, and took postgraduate courses during brief stays at the universities of Leiden, Paris, and Edinburgh. In the mid-1750s, he returned to his hometown, where he set up a medical practice. Ingenhousz also established a laboratory where he performed chemistry and physics experiments.

After his father died in 1764, Ingenhousz used his inheritance to travel throughout Europe for a time before moving to London, England, at the invitation of a longtime family friend, Sir John Pringle, a physician and president of the Royal Society.

In London, Ingenhousz became aware of two scientists and physicians who were making a fortune inoculating wealthy individuals against smallpox. He quickly learned the inoculation technique, which was a revival of an ancient method of combating a virulent, contagious disease that would remain in use until the twentieth century. Using a needle dipped in fluid from the pustule of an infected person, practitioners scratched healthy patients, which made them slightly ill but protected them against the disease and immunized them against further smallpox infections. Ingenhousz practiced this technique first at Foundling Hospital in London.

Ingenhousz’s work soon came to the attention of Holy Roman Empress Maria Theresa, and in 1768 he was invited to Vienna, Austria, to inoculate the royal family.

Life’s Work

In Austria, Ingenhousz successfully inoculated the entire Habsburg family, preventing them from contracting or spreading smallpox. In gratitude, Empress Theresa appointed him court physician, granting him a generous annual income for life. Now a wealthy, independent man fluent in German, Dutch, French, Italian, and English, Ingenhousz moved freely among such European centers of population as Paris, Florence, Geneva, Edinburgh, and London, performing his life-saving work. In 1775, he married Agatha Maria Jacquin in Vienna. Jacquin was the daughter of a Dutch botanist serving the Austrian court. Ingenhousz and his wife produced no children—in fact, they were separated for years at a time as a result of his frequent travels.

In the mid-1770s, Ingenhousz settled in England. He took residence at the estate of Bowood House, in Calne, Wiltshire, as tutor to the children of Dublin-born William Petty-FitzMaurice, Earl of Shelburne, 1st Marquess of Lansdowne, who served as British prime minister from 1782 to 1783. At Bowood, Ingenhousz came into contact with the American diplomat, scientist, and inventor Benjamin Franklin, who would become a lifetime friend and frequent correspondent. Ingenhousz also worked alongside Joseph Priestley—discoverer of the gas that would become known as oxygen—then estate librarian and scientist in residence.

Ingenhousz soon turned away from medicine and toward scientific research. He conducted experiments in chemistry and physics and studied electricity and botany. Ingenhousz was invited to deliver the Bakerian Lectures on physical science to the Royal Society of London in 1778 and 1779. He was elected as a fellow of the society in the latter year.

During the late 1770s, Ingenhousz began building upon Priestley’s botanical studies and performed considerable research on the physiology and character of plant behavior. His work ultimately led to the 1779 publication of his major work, Experiments upon Vegetables, which laid the foundation for an understanding of the process of photosynthesis. The book was translated into several languages and widely distributed throughout Europe.

Though his studies were far ranging (in 1785, he observed the movement of particles of coal dust in fluid, evidence of what was later called Brownian motion), Ingenhousz primarily concentrated on botany during the remainder of his life. In 1782, he published Some Farther Considerations of the Influence of the Vegetable Kingdom on the Animal Creation. Later in the decade (1787 and 1789), he published his two-volume Experiments on Plants, and in 1792 released an essay, “On the Food of Plants and the Renovation of Soils.”

In 1789, Ingenhousz went to Paris to visit fellow scientist Antoine Lavoisier, who had given names to the elements hydrogen and oxygen, and who had performed chemical experiments closely related to Priestley’s and Ingenhousz’s research with plants. Ingenhousz was in Paris when French peasants stormed the Bastille on July fourteenth (afterward known as “Bastille Day”), and had to flee back to London, where he remained for the rest of his life, never again to see his wife in Vienna. Lavoisier, a wealthy aristocrat, was less fortunate: ultimately arrested and imprisoned during the French Revolution, he was guillotined in 1794.

Ingenhousz continued his scientific research until the end of his life. In 1795, he published an important paper on the nutrition of plants. In 1798, he began corresponding with English physician Edward Jenner, whose method of vaccination would later replace the inoculation technique in the fight against smallpox.

Plagued by gallstones and bladder stones during his final years, Ingenhousz died at Bowood House three months before his seventieth birthday. His widowed wife, whom he had not seen for more than a decade, died the following year.

Impact

Although he was a widely recognized figure during the Age of Enlightenment, which spanned most of the eighteenth century, Ingenhousz has since fallen into relative obscurity. Perhaps one reason he remains largely unknown today is that, typical of the era in which he lived, Ingenhousz worked in a number of fields—immunology, biology, botany, chemistry and physics—without specializing in any one area. In addition, Ingenhousz conducted little original research. Like many scientists, he built upon the earlier work of others. His work represented an intermediary stage for further, more definitive studies of various phenomena.

It was left to future historians to give him proper credit for first describing the process of photosynthesis. It would take another half-century before the ability of plants to change electromagnetic power into chemical action was realized. The biochemical process of photosynthesis was not fully understood or named until the late nineteenth century.

Perhaps Ingenhousz’s greatest legacy was his methodical approach to scientific investigation. In the pursuit of qualitative information, he conducted hundreds of experiments, constantly recalibrating the instruments he used—like the eudiometer for measuring changes in gas mixtures—to double-check the accuracy of his studies. His practice of patiently repeating tests in order to eliminate false leads and better define conclusions helped establish standards for modern research.

Bibliography

Fruchtman, Jack, Jr. Atlantic Cousins: Benjamin Franklin and his Visionary Friends. New York: Basic, 2007. Print. Discusses the relationship between Franklin and various European scientists and political leaders, including Ingenhousz, whom Franklin met in England.

Magiels, Geerdt. From Sunlight to Insight: Jan Ingenhousz, the Discovery of Photosynthesis & Science in the Light of Ecology. Rosemead: Academic & Scientific, 2010. Print. Presents an overview of eighteenth-century science, with a particular concentration in the life of Ingenhousz and his experiments that led to the discovery of photosynthesis.

Reed, Howard S. Jan Ingenhousz: Plant Physiologist; with a History of the Discovery of Photosynthesis. Waltham: Chronica Botanica, 1949. Print. Offers an overview of Ingenhousz’s contributions to natural science, especially noting his discoveries related to photosynthesis.