Today, we learn not to cry over spilt medicine. 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.

I'll bet you've never heard of collodion. Yet it was quite common in the last century. You made it by dissolving cellulose nitrate in ether and alcohol. You kept it on your medicine shelf and used it to cover cuts. It hardened into a protective shell that stuck to the skin and covered the wound.

We're interested in collodion because it kept feeding invention. People kept spilling the stuff and inventing things after they did. For example, let's visit John Hyatt in 1863.

Hyatt was looking for a substitute for ivory billiard balls. Even then, the slaughter of elephants had gone far enough to make ivory too expensive. Hyatt cut his finger one night as he worked on a mixture of sawdust and glue.

He put collodion on the cut, but he spilled the bottle. Then he realized he might have what he needed in the tough sheet of plastic that formed when the liquid dried. He found he could improve the result if he used camphor in the mixture instead of ether. He gave us the first celluloid.

He patented celluloid, and we were soon using the stuff to make everything from men's shirt collars to children's toys. But his billiard balls didn't do well. And therein hangs the next part of our story. Collodion is a close relative to gun-cotton, and so was the first celluloid. Hyatt's billiard balls had a nasty inclination to explode under the right conditions.

Ten years later, Alfred Nobel -- inventor of dynamite and founder of the Nobel Prizes -- cut himself while he was working on a better explosive. He too poured collodion on the wound. At four the next morning, it hit him. He could use collodion, which was already explosive, to stabilize nitroglycerin. The result was a vicious explosive called blasting gelatin.

Three years later, Louis Pasteur was trying to save the French silk industry from a disease that was killing off silk worms. Same story. His assistant, Henri Chardonnay, worked late at night. He also spilled a bottle of collodion. The stuff was tacky, but not yet dry, when Chardonnay tried to wipe it up. His rag came away trailing long strands of solidified collodion.

So Chardonnay said, "Aha!" He went on to develop a process for making artificial fibers. He invented an imitation silk that we later improved and gave the name rayon.

Collodion may have been a primitive ancestor of the Band-Aid. But it surely served to spur the imagination. It proved to be a very special muse to 19th-century invention.

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

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Roberts, R.M., Serendipity: Accidental Discoveries in Science. New York: John Wiley & Sons, Inc., 1989, Chapters 15 and 16.