ISOHEMAGGLUTININS 179 



ing to the von Dungern and Hirschfeld theory children of 

 all types are possible in any matings which involve an AB parent. 

 According to the Bernstein theory the following matings never 

 result in children : B x AB, AB x AB, A x AB. In x AB 

 matings A and B children may result but not or AB children. 

 While there is a general acceptance of Bernstein's hypothesis, 

 Snyder says that it is not yet proved beyond all doubt. The 

 student is referred to the studies of Ottenberg (1928) and "Wiener 

 (1930) for a more comprehensive discussion of these two as well 

 as other theories under consideration at the present time. 



Subgroups. — In 1911, von Dungern and Hirschfeld apparently 

 demonstrated by means of agglutinin absorption experiments 

 that individuals having the A factor fall into two subgroups, 

 those that are purely A and those in which the A agglutinogen is 

 linked with a second agglutinogen A'. Likewise, they apparently 

 showed that there are two kinds of group B sera, those contain- 

 ing only the a agglutinins and the other containing the a agglu- 

 tinin always associated with an a' agglutinin. Others* (see 

 Landsteiner, 1928) have shown that many group sera contain 

 a' as well as a and fB agglutinins. 



Importance of Quantitative Difference. — The existence of sub- 

 groups for A has been confirmed by Schiitze (1921), Coca and 

 Klein (1923), Gutherie and Huck (1923) and Landsteiner and 

 Witt (see Landsteiner, 1928). Lattes and Cavazutti (1924) are 

 of the opinion that these results are all due to quantitative dif- 

 ferences in the agglutinability of corpuscles rather than the ex- 

 istence of a third pair of agglutinins and agglutinogens. After 

 carefully investigating the question raised by Lattes and Cava- 

 zutti, Landsteiner (1928) concludes that the evidence at hand 

 warrants the assumption of a'-A' factors. He states, however, 

 that quantitative variations, as suggested by Lattes and Cava- 

 zutti, may account for many blood differences reported in the 

 literature. Table VI, showing the incidence of the third pair of 

 agglutinating factors, is taken for the most part from Simson's 

 (1926) detailed study with some rearrangement of data and an 

 adoption of a uniform nomenclature. These subgroups are also 

 designated as A^ corresponding to A' and Ao here called A, the 

 corresponding agglutinins being a^ and a.- 



*See Supplementary References, p. 192, for papers by Wiener (1941). 



