Apart from the discovery of the human blood groups and the Rhesus factor Landsteiner developed the visualization of Spirochaeta pallida by the method of dark field microscopy. Furthermore, he demonstrated the transmission of poliomyelitis to monkeys, which made it possible to prove the viral origin of this disease. He gave fundamental impulses to the development of immunobiology (e.g. concept of haptens, specificity of antigens etc.).