Mercury thermometers (an invention of Daniel Fahrenheit in 1714) • WIKIMEDIA COMMONS At the beginning of the XVII th century, Santorio Santorio was one of the great names in Italian medicine. During his youth, he began by settling in Croatia, then in Venice to practice medicine, which he then taught at the University of Padua between 1611 and 1624. He finally retired to Venice, where he died in 1636. The measurements, to which he devoted his whole life, earned him a place among the founders of experimental medicine. Most of them focused on his own physiological manifestations, such as his weight, his food consumption or his stool production. For their study, he developed scales, a device for measuring the frequency of pulse beats or pulsometer (pulsologium) , as well as other precision instruments, the most famous of which was the thermometer. A few years earlier, between 1592 and 1603, Galileo had set a precedent:a glass tube containing a heat-sensitive liquid, the expansion or contraction of which caused glass spheres to rise or fall depending on the temperature. However, Galileo's device, now called a "thermoscope", carried no graduated scale and could only be used outdoors. Santorio was the first to develop a graduated thermometer and use it for medical purposes to take body temperature. By mouth or by hand Santorio made his invention known in his Commentaria in artem medicinalem Galeni , published in 1612, but whose imprimatur dates from 1611:"I am going to tell you a wonderful way in which I have become accustomed to measuring, with a certain glass instrument, the cold and hot temperatures of the air in all regions and places, and of all parts of the body, and as exactly as one can measure with a compass the degrees and limits of hot and cold at any time of the day. » Santorio's invention is also mentioned by the Italian physicist and inventor Giovanni Francesco Sagredo, in a letter dated June 30, 1612 addressed to his friend Galileo:"Monsieur Mula, who had gone to the fair, told me that he had seen a Monsieur Santorio measuring hot and cold with a compass, which he described as a glass ball from which a long pipe rose. » Later, in a work printed in 1626, Santorio described and illustrated several models of "thermometers", a term which first appeared that same year in a work by the French Jesuit Jean Leurechon. One of these thermometers was used to estimate the heat of a patient's heart by taking the temperature of his breath, which was then thought to come from this organ. Santorio also designed a thermometer for the mouth, like those of today, and another to be held in the hand. He measured the temperature range indicated by the thermometer by observing the distance traveled by the liquid in the space of 10 oscillations of a small pendulum (the pulsologium ), a method that provides an excellent indicator of fever. Several inventors later perfected the thermometer. In 1714, Daniel Fahrenheit invented the more accurate mercury thermometer, for which he designed the scale that bears his name. At the same time, Herman Boerhaave used this instrument to take the temperature of his patients. In the middle of the 19 th century, the scientific work of Karl Wunderlich on fever made the thermometer indispensable for measuring its different phases, thus helping to generalize its medical use. Timeline Around 1592 Galileo invents a device that detects temperature variations by means of a liquid substance.1611 Santorio imagines the first instrument capable of accurately measuring variations in body temperature.1666-1667 At Oxford, John Locke made indoor observations for medical purposes.1707 Stancari creates the first sealed thermometer. Reduced air pressure allows for more accurate results.1714 Daniel Fahrenheit invents the modern mercury thermometer, to which he later adds his own scale.1742 Anders Celsius records the boiling and freezing temperatures of water, creating another temperature scale.
