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Loewi quit medical practice and turned to pharmacological research (the study of
drugs and their effects on human organs). Over the next 25 years (1895 to 1920) he studied
how different human organs responded to electrical and chemical stimuli. His papers reported on many human organs including the kidney, pancreas, liver, and brain.
By 1920 Loewi was focusing much of his attention on nerves. He was convinced that
chemicals carried signals from one nerve fiber to the next. But, like other researchers, he
couldn’t prove it.
Loewi later said that the answer came to him in a dream. It was the night before Easter
Sunday, 1921. Loewi woke up with a start around midnight and scribbled notes about the
dream’s idea. The next morning he was unable to read his scrawled notes. Nor could he remember what the dream had been about. All he could remember was that the notes and the
dream were critical.
The next night he awoke at 3:00 A.M. from the same dream, remembering it clearly. He
didn’t dare go back to sleep. He rose and drove to his lab, where he performed the simple experiment from his dream—an experiment that has become famous.
Loewi surgically removed the still-beating hearts from two frogs and placed each in its
own container of saline (salt) solution. He left the autonomic nerve (the Vagus nerve) attached to heart number one, but not to the second heart. When he applied a tiny electrical
current to heart number 1’s Vagus nerve, the heart slowed down. When he then allowed
some saline solution from container 1 to flow into container 2, the second heart slowed
down to match the slower rate of the first heart.
Electricity could not have affected the second heart. It had to be some chemical released into the saline solution by heart 1’s Vagus nerve that then communicated with and
controlled heart 2. Loewi had proved that nerve cells communicate with chemicals. Loewi
called this chemical vagusstoff.
A friend of Loewi’s, Englishman Henry Dale, was the first to isolate and decode this
chemical’s structure, which we now call acetylcholine. Dale coined the name
neurotransmitters for this group of chemicals that nerves use for communication.
Fun Facts: The longest nerve cell in your body, the sciatic nerve, runs
from your lower spine to your foot, roughly two to three feet in length!
More to Explore
Adler, Robert. Medical Firsts. New York: John Wiley & Sons, 2004.
Lanzoni, Susan. A Lot of Nerve. New York: Thomson Gale, 2006.
Masters, Roger, ed. The Neurotransmitter Revolution. Cairo: Southern Illinois University Press, 1996.
Valenstein, Elliot. The War of the Soups and the Sparks: The Discovery of
Neurotransmitters and the Dispute Over How Nerves Communicate. New York:
Columbia University Press, 2005.
Webster, Roy. Neurotransmitters, Drugs and Brain Function. New York: John Wiley
& Sons, 2001.