Blood Grouping 409 



mental discoveries in microbiology were taking place in rapid 

 succession, serological procedures were playing an increasingly 

 important role in studies being conducted in the laboratories of 

 that period. 



Karl Landsteiner, an Austrian, observed in 1900-1901 that when 

 different human blood sera were mixed with blood cells of selected 

 human beings, the red cells of some persons clumped together, or 

 agglutinated. Other workers had observed this reaction when the 

 cells of one animal species were treated with the serum of a diff- 

 erent animal species, but Landsteiner was apparently the first in- 

 vestigator to notice the phenomenon within a given species. The 

 name iso-agglutination was applied to this reaction. 



In his study of the first series of twent\'-two different blood 

 samples, Landsteiner discovered three distinct groups of blood on 

 the basis of agglutination reactions. From these findings he postu- 

 lated the presence of two antigens (agglutinogens) and two anti- 

 bodies (agglutinins) in human bloods. He never found a person 

 harboring an antibody that agglutinated his own red blood cells 

 —a finding which might be expected by logical reasoning. 



In 1902 two of his colleagues, von Decastello and Sturli, de- 

 scribed a fourth blood group in which both agglutinogens were 

 present in the same cells and the agglutinins were both absent from 

 the serum. Landsteiner had missed this less prevalent type of 

 blood since he had sampled an insufficient number of cases, and 

 none of his twenty-two subjects happened to belong to this rare 

 group. 



This work on blood types was confirmed by Hektoen in 1907, 

 and in that same year Jansky offered the first definite classification 

 scheme of the four blood groups which he called, I, II, III, and IV. 

 Two years later Moss independently devised a classification scheme 

 in which groups I and IV of Jansky were reversed, but groups II 

 and III remained the same. Because Moss published his findings 

 in a more accessible publication, his scheme for classifying blood 

 was adopted in preference to that of Jansky who had priority. 



It was only natural to expect that confusion would eventually 

 arise between those who read Jansky 's article and those who read 



