Through his psychiatric research, Janský tried to find a correlation between mental diseases and blood diseases. He found no such correlation existed and published a study, Hematologická studie u psychotiků (1907, Hematological study of psychotics), in which he classified blood into four groups, I, II, III, and IV. (At the time, Janský was unaware of the work of Karl Landsteiner, whose discovery of the A, B, and O blood types earned him the Nobel Prize in Physiology or Medicine in 1930.) At the time Janský's discovery passed almost unnoticed. In 1921 an American medical commission acknowledged Janský's classification. A similar classification was described by William Lorenzo Moss, except the I and IV of Moss were the opposite to that of Janský's, leading to confusion in blood transfusion until the use of A, B and O became standard.
Legacy
Frequent voluntary blood donors in the Czech Republic and Slovakia are awarded with Janský medal (Janského plaketa).