Engines of Our Ingenuity

No. 642:
TYNDALL AND GERMS

by John H. Lienhard

Click here for audio of Episode 642.

Today, we cast a new light on disease. 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.

Mary Shelley spent the summer of 1816 in Switzerland. First she read Erasmus Darwin's ideas about the spontaneous generation of life in rotting food. Then she wrote her own story about generating life. She wrote the novel Frankenstein.

Sixty years later, another English visitor summered over in the Swiss Alps. He was the physicist John Tyndall. Like Shelley, he'd also thought about the spontaneous generation of life. In spring, a nearby lake was clean and lifeless. By summer's end it teemed with life. If you weren't careful, he said, you could think that life arose spontaneously in the sterile melted snow.

Today, we know Tyndall for his work with heat, light, and sound. We forget his work on micro-organisms and airborne disease. Yet it stands right along with Pasteur's and Lister's.

He'd begun in the 1860s when he was studying light. He wanted to make air dust-free. So he created the Tyndall Box. He coated the walls inside a sealed box with glycerin.

After 3 days, all the particulates in the air stuck to the walls and left the air in the box clean as a whistle. Tyndall had made the air optically pure. He showed that beams of light are invisible when they enter a window and pass through clean air.

By now doctors knew that dirt and dust caused disease. They also suspected that germs might be major agents of disease. Tyndall put those ideas together. He saw that by cleaning the air he'd removed the vehicle that carries micro-organisms.

To make his point, he exposed test tubes of urine to the clean air in a Tyndall box. Bacterial life grew in the test tubes under normal air. They stayed sterile in the box. So he repeated the experiment with meat, fish, and vegetables. Same story. None of them putrefied in clean air, either.

He made his work public in 1870. Then the fun began. Biologists attacked him. One of them, a believer in spontaneous generation, scalded him for "quitting his own metier." He told Tyndall that the germ theory of disease was the business only of biologists and physicians.

We hear a lot of that today. Don't talk about poetry if you're a historian. You can't understand medicine unless you're an M.D. Tyndall shot back: If that were true, then the chemist Pasteur shouldn't be allowed to study germs.

Tyndall began by studying light. When he was done, he'd pinned down the origin of disease. He brought alien knowledge to biology. He changed biology when he took it into that clever box -- and cast the clean invisible light of his physics upon it.

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

(Theme music)


Tyndall, J., Essays on the Floating-Matter of the Air. (Reprinted from the New York Edition of 1882, R.N. Doetsch, ed.) New York: Johnson Reprint Corp., 1966.

Tyndall is a fascinating and underrated scientist. For more on the man, see Episodes No. 192, 531, and 624.



Image courtesy of Special Collections, UH Library

John Tyndall, from the frontispiece of his book, Forms of Water in Clouds and Rivers, Ice and Glaciers, 1874


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