jun 30, 1902 - Hematology

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Karl Landsteiner discovered that blood did not come in one universally shared type among humans. These types are known as Type A, B, O, and AB. This finding led to more successful blood transfusions, which before this discovery had a higher risk of patients’ immune systems rejecting transfusions and dying. He also suggested that these types of blood could be used in forensics in where blood was left on the scene of the crime.

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