Jan Baptist van Helmont (; ; 12 January 1580 – 30 December 1644) was a chemist, physiologist, and physician from Brussels. He worked during the years just after Paracelsus and the rise of iatrochemistry, and is sometimes considered to be "the founder of pneumatic chemistry". Van Helmont is remembered today largely for his ideas on spontaneous generation, his 5-year willow tree experiment, and his introduction of the word "gas" (from the Greek word chaos) into the vocabulary of science. His name is also found rendered as Jan-Baptiste van Helmont, Johannes Baptista van Helmont, Johann Baptista von Helmont, Joan Baptista van Helmont, and other minor variants switching between von and van. Early life and education 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. Career as chemistry pioneer 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. For Van Helmont, air and water were the two primitive elements. Fire he explicitly denied to be an element, and earth