Kekulé's dream gave an image, Ramanujan's dreams gave formulae – but the case of Otto Loewi is one step more astonishing still: his dream delivered a complete, workable experiment. He got up in the middle of the night, went to the laboratory – and what he dreamed led, in 1936, to the Nobel Prize. Sounds too good? That is exactly why it pays to look closely: what did the dream really achieve, and what was already there beforehand?
The dispute: "soups or sparks"
Otto Loewi (1873–1961), a German-born pharmacologist who long worked in Graz, faced one of the great open problems of physiology: how does a nerve speak to the organ it controls? Is the transmission purely electrical (the "sparks") or via a chemical messenger (the "soups")? Around 1920 this was fiercely contested, and no one had a clean proof. Loewi himself had had the idea of chemical transmission years earlier (around 1903) – he simply lacked a way to test it.
The two nights
Sleep supplied the way. In his autobiographical sketch (1960) Loewi tells the story himself – it takes place on the night before Easter (traditionally dated to 1921):
"The night before Easter Sunday I awoke, turned on the light and jotted down a few notes on a tiny slip of paper. Then I fell asleep again. It occurred to me at six o'clock in the morning that during the night I had written down something most important – but I was unable to decipher the scrawl. The next night, at three o'clock, the idea returned. This time I got up at once, went to the laboratory, and performed the experiment on the frog's heart."
It is this double night – the lost first note and the returning inspiration – that makes the story so unforgettable. Loewi did not wait for morning; he knew the idea might otherwise slip away from him a second time.
The two-frog-heart experiment
The experiment is of striking simplicity. Loewi prepared two beating frog hearts in nutrient solution. On the first he left the vagus nerve intact and stimulated it – the heart slowed, as expected. He then took the fluid that had bathed this first heart and transferred it to the second heart, which had no stimulated nerve at all. And this second heart, too, slowed down.
With that it was proven: the vagus stimulation had released a chemical substance into the fluid that carried the effect. Loewi at first simply called it "Vagusstoff" (vagus substance). Later it was identified as acetylcholine – the first known neurotransmitter. A corresponding accelerating substance from sympathetic stimulation ("Acceleransstoff") pointed towards adrenaline.
The consequences
Loewi's night-time experiment became the founding experiment of neuropharmacology. It settled a good part of the "soups versus sparks" dispute in favour of chemistry (the full picture includes both) and laid the foundation for understanding how almost all of today's psychiatric drugs and many medicines work: through chemical signalling at the synapses. In 1936 Loewi, together with the Briton Henry Dale, received the Nobel Prize in Physiology or Medicine "for their discoveries relating to chemical transmission of nerve impulses".
The honest framing
As good as the story is, it calls for three sober clarifications – and none diminishes it.
- The dream supplied the experiment, not the hypothesis. Loewi had been carrying the idea of chemical transmission around with him for some 17 years. The dream gave him not the thought but the decisive experimental design to test it at last. This is a textbook case of incubation: a long-prepared mind receives, in half-sleep, the missing form.
- The first attempt was finicky. In its raw first version the experiment succeeded only under favourable conditions (temperature, season, species of frog); colleagues at first struggled to reproduce it, and Loewi himself admitted he had been lucky. Only the later refinement made the finding robust and incontestable.
- He told it late. As with Kekulé, the embellished dream account comes from hindsight (1960, almost four decades later). That does not make the core – a night-time idea, immediately put into practice – implausible, but it counsels caution about the details.
What remains
Loewi is the strongest case in the small cluster around Kekulé, Tesla and Ramanujan – because, unlike an image or a formula, his inspiration was immediately testable and passed the test (after refinement). Therein lies the lesson, the same one Kekulé formulated: the unconscious can supply a hypothesis or even a whole experiment – but only the waking laboratory decides whether it holds. Dreaming and testing are not opposites but two steps of the same discovery.
That creative insight should so often take the detour through an image-laden, half-conscious state before the discursive intellect catches up remains remarkable – no proof of anything supernatural, but an honest reminder of how little we know about the source of such ideas. More on the underlying question in our piece on the assumption that the brain produces consciousness.
Sources:
• Otto Loewi, An Autobiographic Sketch, Perspectives in Biology and Medicine 4(1), 1960, pp. 3–25 – the primary source of the dream account in Loewi's own words.
• Otto Loewi, Über humorale Übertragbarkeit der Herznervenwirkung. I. Mitteilung, Pflügers Archiv für die gesamte Physiologie 189, 1921, pp. 239–242 – the original experiment.
• Elliot S. Valenstein, The War of the Soups and the Sparks. The Discovery of Neurotransmitters and the Dispute Over How Nerves Communicate, Columbia University Press, New York 2005 (ISBN 978-0-231-13589-4) – the historical framing of the "soups versus sparks" dispute.
• Nobelprize.org, The Nobel Prize in Physiology or Medicine 1936 (Loewi & Dale).
Continue in our curated knowledge collection – see also the sister articles on Kekulé's benzene ring dream, on Nikola Tesla's visions and on Ramanujan and the goddess Namagiri, as well as on the question of brain and consciousness.