The man who invented the electrocardiogram was born on this day in 1860.
In 1903, Dutch physiologist Willem Einthoven devised the Einthoven galvanometer, an instrument that allowed him to measure and record on graph paper changes in electrical potential as heart muscle contracts. He used the technique on patients from 1908 to 1913, learning how to spot deviations in the recordings--for which he coined the term "electrocardiograms"--that signaled different kinds of heart disease.
Einthoven experimented with various electrode arrangements and came up with the standard limb leads still in use today. His work earned him the 1924 Nobel Prize in physiology or medicine. He died in 1927.
[SOURCE: BRITANNICA ONLINE]