“Loewi soon figured out that his vagusstoff was a well-known chemical called acetylcholine. We now say that acetylcholine, or ACh, is a transmitter substance, or neurotransmitter, because it functions to carry neural messages across the synapse. ACh is found throughout the nervous system and has a generally excitatory action, though it causes the opposite effect in the heart. One of its most important functions is to convey excitatory messages from your motor nerves to your skeletal muscles. Whenever you reach for a pen on your desk or scratch an itchy place on your scalp or move any part of your body, your movements are the end result of the stimulation of muscles by the release of tiny amounts of acetylcholine at synapses called neuromuscular junctions—the junctions between the motor nerves and skeletal muscles.

“If you look out to the left, you will see I’ve managed to trap an acetylcholine molecule exactly like the ones that Loewi transferred from one frog heart to the other.” Mindstein says.