A clinical thermometer is a thermometer used to measure human body temperature. Most made in the 20th century are mercury-in-glass thermometers. They are accurate and sensitive, having a narrow place where the mercury level rises very fast. A kink in the tube stops the mercury level from falling on its own.
These thermometers are used in clinics by doctors, so they are also called a doctor's thermometers or medical thermometers. Most show both Celsius scale and Fahrenheit temperature scales, and run from 35 degree Celsius to 42 degree Celsius.
Medical thermometers are cleaned before and after each use, with alcohol.
For centuries medical thermometers were large, and took many minutes to register a temperature. In the 1860s smaller, better ones were made, and thus thermometers were more often used. An ear thermometer was invented in the 1960s, which works quickly and easily. Digital thermometers became widespread in the late 20th century.