This slide shows the results of an experiment that mixed the cellular and liquid components of blood. Landsteiner separated the cellular and liquid components of blood from both his colleagues and himself, and mixed them in different combinations. He then observed the agglutination of red blood cells (RBC) in certain combinations, as indicated by the plus (+) symbols in the table. He also observed the absence of agglutination in the other combinations, as indicated by the minus (-) symbols. When cellular and liquid components from the same individuals were combined, no RBC agglutination was observed. If RBC agglutination occurs in the human body, it was expected that capillaries would be clogged and adverse effects would be elicited. Therefore, Landsteiner’s experiment showed for the first time that blood transfusion has to be performed in a combination where no RBCs are agglutinated. This discovery subsequently led to the development of safe medical practices regarding blood transfusion. Additionally, the results also showed that individuals can be grouped based on agglutination patterns. In the table shown here, Dr. Pleen. and Mr. Zar. belong to one group, Dr. Sturl. and Dr. Erdh. belong to another, and Dr. St. and Mr. Landsteiner belong to the third group. In the following year, the fourth group was found by Landsteiner’s disciples, and these 4 groups became the ABO blood group system.