Body temperature is one of the most important indicators of the condition of the body. In modern medicine, temperature measurement is an elementary action. And everyone can do it at home, thanks to the availability of simple thermometers. But up to a certain point, thermometers did not exist. How to determine the temperature of the body in the past?
History of the invention of the thermometer
A single inventor of this device is difficult to establish. The fact is that several scientists tried to create a device that would allow us to recognize the temperature of the human body, air, water, and ground. It is a credit to such famous people as Galileo Galilei, Santorio, Robert Fludd, Lord Bacon, Salomon de Coss, and others.
The very first mention of the creation of the instrument is because of Galileo Galilei. He did not describe the thermometer in his writings, but the physicist’s pupils confirmed that as early as 1597 he created a prototype of the modern thermometer – a thermoscope. Its principle of operation was almost the same, but instead of mercury, water, and air were used.

A glass tube with a ball on top was placed in a vessel with water. When heated, the liquid rose from the tube because of the expansion of air. As it cooled, the water went down.
In mercury thermometers, for example, heating promoted the expansion of the mercury. Galileo’s invention had no scale, so the temperature could only be judged subjectively. In addition, he did not set out to invent the medical thermometer specifically.
A thermometer with marks, which could be used for medical, was developed in 1626 by Santorio, an Italian physician concerned with anatomy and physiology. However, his device was extremely oversized – so big that it could only be installed outdoors.
Attempts of other scientists ended up with approximately the same success. One thing their inventions had in common was that the readings were unreliable. They contained air, and the temperature depended on atmospheric pressure.
It would seem that the problem could be solved with water, but at low temperatures, it would freeze and the device would burst. Then the inventors guessed to use alcohol. Of course, it was not the final variant, but the device was quite usable. The only thing that remained to be decided was the scale.
Fahrenheit, after whom the temperature scale was later named, turned out to be the most optimal solution. It was also Fahrenheit the preferred to use mercury. His scale had three reference points: 0, 32, and 212 degrees, which corresponded to the temperature of certain mixtures and the boiling point of water.
Interesting fact: the entire world can thank Anders Celsius, the Swedish astronomer, for the thermometer of the modern type with the familiar scale. In 1842, he proposed his scale. It has two points – the temperature of boiling (100 degrees) and freezing (0 degrees) of water.

Measuring temperature without a thermometer
The medicine of the past paid minimal attention to diagnosis. Doctors did not seek to conduct examinations, take and study tests, and measure the temperature of patients. Thermometry was considered a useless activity. Although the first prototypes of thermometers appeared as early as the 16th century, no one used them for medical purposes for many years.
Doctors of this era were guided only by minimal examination. They measured the pulse, examined the general condition of patients, and inquired about their well-being and medical history – again, from the patient’s words. If they tried to measure the patient’s temperature, they only did so by putting their hand on the patient’s forehead. Based on their findings, they made diagnoses and prescribed treatment.
Despite the emergence of the thermometer, it is not soon used in medicine. For example, there is evidence that even at the end of the 19th century, some physicians had a negative attitude toward thermometry. Some considered the use of devices too complicated, and some were convinced that a proper doctor did not need accurate numerical data.
The first thermometers appeared in the 16th century. They had a lot of flaws, but they served as the prototype for modern devices. There is no single inventor of the thermometer, but the appearance of the device is associated with famous scientists: Galileo Galilei, Santorio, Robert Fludd, Lord Bacon, Salomon de Cosse, and others. They all made some contributions to the creation of the thermometer. However, it was not rushed into medical use until the 20th century. Thermometry was complicated and unnecessary. Body temperature was measured by touch – by putting a hand on the patient’s forehead.