History of the Thermometer

The temperature of the human body has been used as a diagnostic sign since the earliest days of clinical medicine. The earliest thermal instruments were developed during the sixteenth and seventeenth centuries. In 1665, it was suggested that the melting point of ice and the boiling point of water should be the standard. The most common scales today are the Fahrenheit, Centigrade, and the Kelvin scales. Since the earliest days of medicine, physicians have recognized that the human body can exhibit an abnormal rise in temperature, usually defined as fever, as an obvious symptom of illnesses. In 1868, Wunderlich established that the temperature in a healthy person is constant and that variation of temperature occurs in disease. The Allbutt thermometer was the first practical device to become commercially available. The technology has then improved to provide highly accurate devices, for example, thermal imaging; its use is still growing in medicine.