Last modified on Thu 10 Dec 2020 14.41 EST
In 1955 the physiologist Otto Hutter, who has died aged 96, was studying the pacemaker cells to be found in the heart. These produce the electrical impulses that fire the muscle’s contractions. At the time it was not clear why these electrical impulses should fluctuate, but in a set of extraordinary photographs Hutter and his colleague Wolfgang Trautwein captured the trace from the pacemaker cells showing what happened when different nerves in the body were stimulated.
The photographs, which became a standard feature in medical textbooks, showed that when the vagus nerve, running from the brain stem to the colon, was stimulated, the waves of electrical activity in the pacemaker cells died down, and when the sympathetic nerves, responding to stress, were activated, they increased.