Larry Tend is, age 11, of Los Angeles Cal for his question:
Who invented the medical thermometer?
Come spring, a number of us are sure to go down with colds or flu! Then is the time to bring out the medical, or clinical thermometer. Place the little glass tube under the tongue, close the mouth and shut off all conversation for two or three minutes. Now study the fine dark line of mercury inside the glass tube. If it has risen high above the red arrow at 98.6 degrees Fahrenheit, you are as sick as you feel. Call the doctor and report the facts.
The normal temperature of the human body ranges from a little below to a little above 98.6 Fahrenheit degrees. When the body is battling an infection, this temperature rises and we have a fever. Naturally, we stay in bad and keep warm while the body is occupied in defending itself.
Doctors from earliest times have known that the body gets hot and feverish when the patient is sick. But they did not know how to get the accurate facts on this until about 200 years ago. The first clinical thermometer was made by Gabriel Fahrenheit. We honor him by using his name for the Fahrenheit temperature scale. He used a bulb of mercury firmed to a narrow bore in a glass tube. This instrument was somewhat crude but the principle was the same as in our own more refined thermometers.
Mercury, like most things, expands when heated. When the mercury in Fahrenheit's glass bulb was warmed, it ran up into the narrow bore in the glass tube. The more it was warmed, the higher it rose. The first information given by this thermometer was that this thing is warmer ar cooler than that. The next fob was to find how much cooler or warmer. Fahrenheit did this by working out a scale of temperature in degrees.
For the bottom of his scale, he chose the coldest thing known at the time a mixture of salt and water. He dipped the thermometer into this chilly mixture and, where the column of mercury stopped falling, he put a zero mark. Then he took his own temperature and where the mercury stopped rising he put a mark which he called 96.
The space between the zero mark and the 96 mark was then divided into a ladder of degrees. Fahrenheit then added more equal degree marks above and below. He discovered that water freezes at 32 degrees on his temperature scale and boils at 212 degrees. Later, the human temperature was taken more accurately and found to be normally around 98.6 degrees on Fahrenheitts temperature scale.
We still use the Fahrenheit scale on our clinical thermometers and for the weather. The centigrade scale is more simple. It is based on the freezing and the boiling points of water. The scale between these two points is divided neatly into 100 degrees.