“In Medicine, he introduced the examination of the specific gravity of urine for diagnostic purposes. He investigated the fluids in the human body and advanced the study of digestion and other physiological changes by discovering acid digestion in the stomach, coming close to identifying gastric acid with hydrochloric acid some two hundred years before the actual discovery of this fact. He also appreciated the significance of bile in the gut digestion.
Helmont’s significance in the development of chemistry is perhaps even greater; he was the first to use the term ‘gas’. He realized that ‘gas’ was distinct from air and water vapour, and he distinguished the ‘gases’ derived from various sources, including that which we call carbon dioxide.” (PMM 135).

Edited by his son and published posthumously, the present work established his name as one of the founders of biochemistry: “His discovery of digestive juices in the stomach and intestine, and especially his first use of the specific gravity of urine for diagnostic purposes, mark him as a man of no insignificant importance in the history of medicine”. (Heirs of Hippocrates)

Johann Baptist von Helmont (1577-1644) was a Flemish chemist, physiologist, and physician known for his pioneering work in early chemistry and medicine. He is often considered one of the founders of modern chemistry and was a significant figure in the transition from alchemy to chemistry: "Helmont devoted his life to exploring the first principles of nature through chemistry. He is best remembered as the discoverer of gas, a term he coined to describe the 'specific smokes' that remain after the combustion of solids and fluids; among the gases he identified were carbon dioxide, carbon monoxide, chlorine gas and sulphur dioxide.

He denied that metals dissolved in acid were either destroyed or transmuted, stating that such metals were recoverable in their original quantities, and correctly identifying the process of precipitation. Like Paracelsus, he rejected traditional humoral pathology and advocated an ontological concept of disease, regarding each disease as a specific entity caused by a specific pathogenic agent. He demonstrated that acid is the agent in animal digestion and came near to identifying it as hydrochloric acid; he also identified the causes of asthma and correctly described fever as a part of the body's natural healing process.” (Norman 1048)

Though separately paginated, 'Opuscula medica inaudita' is considered a part of the whole volume. Originally published as a separate work in 1644, 'Opuscula medica inaudita' contains reprints of Helmont's treatises on the stone, on fevers, on the errors of humoral pathology, and on the plague" (Norman 1048).
'Ortus Medicinae' was translated into English by Christopher Packe in 1662.

PMM 135
Heirs of Hippocrates 254
Osler 2929
Norman 1048
Garrison & Morton 665
Wellcome III, p. 241