Blood Types
Year of Discovery: 1897
What Is It? Humans have different types of blood that are not all compatible.
Who Discovered It? Karl Landsteiner
Why Is This One of the 100 Greatest?
Blood was blood—or so the world thought. Then Austrian physician Karl Landsteiner
discovered that there were four types of blood. Some could be safely mixed and some could
not. That discovery has saved millions of lives. The day that Karl Landsteiner’s results were
published, blood transfusions became a safe and risk-free part of surgery. A patient’s
chances of surviving surgical procedures greatly increased. By making surgery safer, he
made many new surgical procedures possible and practical.
Landsteiner’s discovery also greatly advanced human understanding of blood structure and blood chemistry and paved the way for a number of key medical discoveries in the
early twentieth century.
How Was It Discovered?
Vienna, Austria, was a glamorous city in 1897—as modern as any in the world. Dr.
Karl Landsteiner worked in the University of Vienna hospital, where he conducted
cause-of-death (post mortem) medical examinations.
One April day that year, Landsteiner examined four patients who had died during surgery. All died for the same reason: blood agglutination (clotting). Each patient had received
blood transfusions and died when his or her own red blood cells clumped together with red
blood cells in the blood they were given into thick clots.
Landsteiner had seen this often during his thousands of post mortem examinations and
wondered why it only happened with some patients.
That evening, Landsteiner played piano for his wife and several friends. It was the one
thing Karl felt he did well. Most who heard him thought he should give up medicine for a
brilliant career as a pianist.
In the middle of a familiar piece, it suddenly occurred to Landsteiner that the answer
had to be something in the patients’ blood. What if all blood was not the same, as everyone
supposed?
The next morning Landsteiner collected blood from 20 patients, wanting to see if he
could predict which samples were safe to mix with each other.
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