It was on June 25, 1943 that the world lost a great mind and a great medical scientist, when Dr. Karl Landsteiner succumbed to the effects of a heart attack that had overtaken him two days before while he was actively at work in his laboratory. He had just passed his seventy-fifth birthday of a lifetime devoted to fundamental research. Shortly before his death he had completed the second edition of his classic book, “The Specificity of Serological Reactions”, and he had also published almost 350 scientific papers describing the results of his pioneering investigations. This year is the centenary of the birth of Karl Landsteiner, and it seems fitting at this time to pay tribute to this genius and benefactor of mankind by reviewing some of his great discoveries.

Of Dr. Landsteiner's discoveries, the one that has captivated the popular imagination the most is his discovery of the A-B-O blood groups, frequently called the Landsteiner blood groups in his honor. At the beginning of the present century, it was recognized that bloods from animals of different species could be distinguished from one another by their serological reactions. For this reason, the use of animal blood for transfusions to human beings was abandoned, but the frequent serious reactions that followed transfusions of blood from one human being to another still remained unexplained. Landsteiner then tested the blood of workers in his laboratory by mixing serum taken from one individual with the red cells of others. He found that instead of the weak or negative reactions that might have been expected, in some combinations strong agglutination of the red cells occurred, while in other combinations no effect was apparent.