Singing the Body Electric

Over at the Loom, Carl Zimmer reflects on 18th century science, lightning, and the nervous system. The question of when scientists first realized that our nerves used the same stuff as lightning bolts - a completely outlandish idea - has long fascinated me. It's an empirical story in which two great Italian scientists - Count Alessandro Giuseppe Antonio Anastasio Volta and Luigi Galvani - engaged in a bitter argument about the interpretation of a classic experiment. Volta was right about the experiment, but Galvani was right about the biology.

The story begins in the early 1780's, when Galvani was playing around with Leyden jars, a primitive capacitor. Galvani noticed that touching a charged piece of metal to the leg of a dead frog caused the muscles to flex and sparks to leap. Galvani concluded that the frog contained some sort of "animal electricity," which was secreted by the brain, traveled through the nerves, and led to the instantaneous activation of muscles. The metal was simply conducting the charge contained inside the animal. This was a brilliant, if surreal, hypothesis.

Enter Count Volta. By the 1780's, Volta was already a famous scientist, as he had invented a static electricity machine and isolated methane gas. After hearing about Galvani's experiments, Volta turned his attention to "animal electricity". A devout experimentalist, Volta was skeptical of Galvani's claims; to him, they smacked of the supernatural. By 1794, Volta had begun designing experiments that would falsify Galvani's theory. While Galvani argued that the current originated inside the frog's leg, Volta believed that the current was merely passing through the flesh. To prove his point, Volta replicated Galvani's experiment, but left out the dead amphibian. He found that he could still generate an electrical current just by using metals, and therefore maintained that animal electricity was a fiction. There was no such thing.

Volta won the argument. For the first decades of the 19th century, animal electricity remained the stuff of Frankenstein and gothic horror novels. Since scientists couldn't measure animal electricity, they assumed it didn't exist. That all changed in 1821, with the invention of the galvanometer, a device capable of measuring minor voltages. In 1842, the German physiologist Emil du Bois-Reymond decided to investigate the Volta-Galvani controversy, and used the galvanometer to look for electricity in the leg of a living frog. To his amazement, frog muscle caused a small but consistent activation in the galvanometer. Reymond declared that Galvani was right: our flesh was charged.

Nevertheless, Reymond's experiments were treated skeptically. Animal electricity still seemed too strange to be true. Besides, where did the electricity come from? It's not like the body had a battery.

The experiment cruces came in 1875, when Richard Caton used Reymond's recording technique to measure the electric activity inside the brains of rabbits, dogs and monkeys. His procedure was brutal - live animals had their skulls removed - but the data was clear: the animal brain was teeming with electricity.

To this tangled story of empiricism, I'd like to add a little footnote. (This is actually a footnote in my upcoming book, Proust Was A Neuroscientist.) In 1855, twenty years before Caton resolved the controversy, Walt Whitman wrote an erotic poem about the glories of the body entitled "I Sing the Body Electric". Although the scientists still had their doubts, Whitman didn't. Like Galvani, he just knew: our body is really electric.