Jan Baptist van Helmont

• Born — 12 January 1580 • Birthplace — Brussels, Spanish Netherlands (present-day Belgium) • Died — 30 December 1644 • Place of death — Vilvoorde, Spanish Netherlands (present-day Belgium) • Field — Chemistry, physiology, medicine • Education — University of Leuven • Academic Advisors — Martin Delrio • Known for — Pneumatic chemistry

Jan Baptist van Helmont was the youngest of five children of Maria (van) Stassaert and Christiaen van Helmont, a public prosecutor and Brussels council member, who had married in the Sint-Goedele church in 1567. He was educated at Leuven, and after ranging restlessly from one science to another and finding satisfaction in none, turned to medicine. He interrupted his studies, and for a few years he traveled through Switzerland, Italy, France, Germany, and England. Returning to his own country, van Helmont obtained a medical degree in 1599. He practiced at Antwerp at the time of the great plague in 1605, after which he wrote a book titled De Peste (On Plague), which was reviewed by Newton in 1667. In 1609 he finally obtained his doctoral degree in medicine. The same year he married Margaret van Ranst, who was of a wealthy noble family. Van Helmont and Margaret lived in Vilvoorde, near Brussels, and had six or seven children. The inheritance of his wife enabled him to retire early from his medical practice and occupy himself with chemical experiments until his death on 30 December 1644.

• Illustration — Jan Baptist van Helmont (left) and his son Franciscus-Mercurius, from the Ortus medicinae (first published posthumously in 1648)

Van Helmont was a disciple of the mystic and alchemist, Paracelsus, though he scornfully repudiated the errors of most contemporary authorities, including Paracelsus. On the other hand, he engaged in the new learning based on experimentation that was producing men like Santorio Santori, William Harvey, Galileo Galilei, and Francis Bacon. He made the first proposal of a randomized controlled trial, to test two treatment regimes of fever, in the posthumously published Ortus Medicinae (1648). One treatment would be conducted by practitioners of Galenic medicine involving bloodletting and purging, and the other would be conducted by van Helmont. It is likely that he never conducted the trial, and merely proposed it as an experiment that could be conducted. Let us take from the itinerants’ hospitals, from the camps or from elsewhere 200 or 500 poor people with fevers, pleurisy etc. and divide them in two: let us cast lots so that one half of them fall to me and the other half to you. I shall cure them without blood-letting or perceptible purging, you will do so according to your knowledge (nor do I even hold you to your boast of abstaining from phlebotomy or purging) and we shall see how many funerals each of us will have: the outcome of the contest shall be the reward of 300 florins deposited by each of us.... when there is contradiction, of the two proposals only one is true. (Ortus, pp 526–7)

• Illustration — Title page of Ortus medicinae

Van Helmont was a careful observer of nature; his analysis of data gathered in his experiments suggests that he had a concept of the conservation of mass. He was an early experimenter in seeking to determine how plants gain mass.

For Van Helmont, air and water were the two primitive elements. Fire he explicitly denied to be an element, nor could earth be called a true element because, he argued, it could be reduced to water.

• Illustration — Posthumous portrait of van Helmont Van Helmont is regarded as the founder of pneumatic chemistry, as he was the first to understand that there are gases distinct in kind from atmospheric air and furthermore invented the word "gas". He derived the word gas from the Greek word chaos (χᾰ́ος).

He perceived that his "gas sylvestre" (carbon dioxide) given off by burning charcoal, was the same as that produced by fermenting must, a gas which sometimes renders the air of caves unbreathable.

Van Helmont wrote extensively on the subject of digestion. In Oriatrike or Physick Refined (1662, an English translation of Ortus medicinae), van Helmont considered earlier ideas on the subject, such as food being digested through the body's internal heat. But if that were so, he asked, how could cold-blooded animals live? His own opinion was that digestion was aided by a chemical reagent, or "ferment", within the body, such as inside the stomach. Harré suggests that van Helmont's theory was "very near to our modern concept of an enzyme". Van Helmont proposed and described six different stages of digestion.

Helmont's experiment on a willow tree has been considered among the earliest quantitative studies on plant nutrition and growth and as a milestone in the history of biology. The experiment was only published posthumously in Ortus Medicinae (1648) and may have been inspired by similar experiments by Santorio, published in Ars de statica medicina (1614). Helmont grew a willow tree and measured the amount of soil, the weight of the tree and the water he added. After five years the plant had gained about 164 lbs (74 kg). Since the amount of soil was nearly the same as it had been when he started his experiment (it lost only 57 grams), he deduced that the tree's weight gain had come entirely from water.

Van Helmont described a recipe for the spontaneous generation of mice (a piece of dirty cloth plus wheat for 21 days) and scorpions (basil, placed between two bricks and left in sunlight). His notes suggest he may have attempted to do these things.

In 2003, the historian Lisa Jardine proposed that a portrait held in the collections of the Natural History Museum, London, traditionally identified as John Ray, might represent Robert Hooke. Jardine's hypothesis was subsequently disproved by William B. Jensen of the University of Cincinnati and by the German researcher Andreas Pechtl of Johannes Gutenberg University of Mainz, who showed that the portrait in fact depicts van Helmont.

The authorities additionally record the headings Jan Baptista van Helmont, Johann Baptist van Helmont, Jean Baptist van Helmont and Jean Baptiste van Helmont. His recorded languages were Latin and Dutch. One child is recorded: Franciscus Mercurius van Helmont.