Engines of Our Ingenuity

No. 512:
FEVER THERMOMETERS

by John H. Lienhard

Click here for audio of Episode 512.

Today, a medical instrument enters our lives. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

In grade school, I found being sick was a great way to play hookey. "I'm sick," I'd tell my mother. "Oh? Let's see!" she'd say, driving a thermometer into my mouth.

At first the thermometer beat me. Then I had an idea. I lay it on the radiator for a moment. It worked the first time. The second time, it exploded and blew mercury all over the room. I had to give up and go back to school.

Fever thermometers were the great tool of home diagnosis by the 1930s. By then they'd been in use for only about 60 years.

Temperature itself was part of diagnosis as far back as we have any record. Egyptian doctors laid their hands on patients to see if they were hot or cold. But the tiny temperature changes our bodies can tolerate are hard to measure. We've had thermometers for only 300 years. They've been accurate enough to diagnose fever only since the last century.

We didn't even know how constant body temperatures are until the 1700s. One 100-degree day, Ben Franklin reported that his body stayed at 96 degrees. The fact he didn't measure 98.6 doesn't mean he was cold-blooded. It just means his measurements were inaccurate.

Temperature is hard to measure. As late as 1852, a physician measured the temperature of urine from ten healthy sailors. He got numbers from 102 to 104 degrees. We didn't have accurate studies of our body temperature until the 1860s.

Even then, thermometers had problems. The matter came to a head in the New York Academy of Medicine. One doctor said that "a physician without a thermometer was like a blind man walking the streets." When we're attracted to novelty, said another, we lose the way to truth. We're in trouble when we lose physical contact with the patient.

That was conflict over the two opposing means we use to gather information. Some of us trust the senses to inform us. Some of us feel we have to distance ourselves from our senses.

Doctors who saw their patients in very human terms resisted the thermometer. That's been true of every new clinical aid: forceps for delivering children, anesthesia, and so on. Each has advanced medical mercy. But, at first, each has given doctors a new way to isolate themselves from patients as well.

So I go back to childhood. My mother used the thermometer to express her care for me. I used it to deceive that care. The same tension runs through the childhood of all new medical technologies. Not until we carry our own humanity into them can they can serve us fully.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Dominguez, E.A., and Bar-Sela, A., Adoption of Thermometry into Clinical Practice in the United States. Reviews of Infectious Diseases, Vol. 9, No. 6, November-December 1987, pp. 1193-1201.





The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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