loewi woke and wrote the design on a slip of paper beside the bed. then he went back to sleep. at six, he knew the note held something of great importance, but he could not read his writing. he had captured the dream, but not clearly enough to use it.
the next night, at three o’clock, the idea returned. this time i did not take any risk; i got up immediately, went to the laboratory, and performed a simple experiment on a frog heart.
the design used two frog hearts beating in fluid. loewi stimulated the vagus nerve of the first heart, which slowed its beat. he then moved that fluid to the second heart without transferring a nerve or electrical connection. the second heart also slowed. a substance in the fluid had carried the signal.
loewi called the substance vagusstoff. it is now known as acetylcholine, the first neurotransmitter demonstrated. in 1936, he shared the nobel prize in physiology or medicine with henry dale. loewi wrote the dream account more than once and included the first unreadable note.
the first note shows a practical limit: capture alone is not enough. a record must also be clear enough to use after waking. loewi got a second chance the next night. do not depend on a second chance.