Today, Google is celebrating what would have been the 159th birthday of Willem Einthoven with a special Doodle.
Einthoven was a Dutch physiologist who is best known for inventing the first electrocardiograph (ECG) - a simple test used to check the heart’s rhythm and electrical activity.
ECGs are carried out daily by doctors around the world, and are likely responsible for saving millions of lives.
To celebrate, Google has launched a Doodle, featuring a cartoon depiction of Einthoven, as well as his ECG machine.
Who was Willem Einthoven?
Willem Einthoven was born on May 21 1860, and spent most of his life in the Netherlands.
He studied medicine at the University of Utrecht, before going on to teach at the University of Leiden in 1886.
In 1903, he invented an instrument known as the Einthoven galvanometer, which could measure and chart the changes of electrical potential caused by contractions of the heart muscle.
He coined this process an ‘electrocardiogram’.
From 1908 to 1913, Einthoven studied the patterns of recordings of normal heart activity. This allowed him to recognises when, and why, deviations occurred.
What is he best known for?
In 1924, Einthoven was awarded the Nobel Prize for Physiology or Medicine for his discovery of electrical properties of the heart.
He discovered these properties using the electrocardiograph - a practical instrument that is still used today to diagnose heart disease.
What is an ECG?
The NHS website explains: “An electrocardiogram (ECG) is a simple test that can be used to check your heart's rhythm and electrical activity.
“Sensors attached to the skin are used to detect the electrical signals produced by your heart each time it beats.
“These signals are recorded by a machine and are looked at by a doctor to see if they're unusual.”
How is Google celebrating Einthoven?
To celebrate what would have been the 159th birthday of Einthoven, Google has launched a special Doodle.
The Doodle features a cartoon of Einthoven, as well as his ECG machine, and a print-out of a reading.