9.3  Checking her temperature

Body temperature is a measurement of how hot or cold the internal tissues of the body are. Although it varies a little bit in hot or cold weather, or if the person is wearing too many or too few clothes, or doing heavy physical work, it generally stays close to a value known as ‘normal’ temperature, unless the person is ill. Body temperature is measured using an instrument called a thermometer (Figure 9.2a), which has a ‘bulb’ at one end, usually filled with a silver liquid metal called mercury. (Some glass thermometers contain a red dye instead, and some use digital technology — see Figure 9.2b.) In a glass thermometer, when the bulb of mercury is warmed by a person’s body, the mercury expands and rises up the thin glass tube, which is marked with numbers showing the person’s body temperature.

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Figure 9.2  (a) Glass thermometers may measure temperature in degrees Celsius (top) or Fahrenheit (below). (b) A digital thermometer shows the temperature as a number in a window.

Healthy temperature

Normal temperature is close to 37°C, or just under 98°F. The woman does not feel hot to touch.

Warning sign

The woman has a fever — a temperature of above 37.5°C (or 100°F) or above. She feels hot to touch.

Figure 9.3  You can easily feel if she is hotter than you.