BLOOD GROUPS, HETEROGENETIC ANTIGENS 491 



Landsteiner, Miller and Levine, and we shall refer to them again in a later 

 chapter, where we shall discuss the use of serological methods in the estab- 

 lishment of individual differences in several species of animals. 



Various phases may be distinguished in these investigations into the oc- 

 currence of blood-group differentials and agglutinins in human and animal 

 cells and sera. At first it appeared as though the blood-group differentials in 

 man and in certain animals were identical ; then certain differences were 

 found and doubts arose as to whether the identity was complete. Thus von 

 Dungern and Hirszfeld observed that human beta sera are not only absorbed 

 by human B corpuscles, but also by B corpuscles of various animal species. 

 But subsequently it was discovered that the beta agglutinin of these animal 

 sera cannot be absorbed in a corresponding manner by B human and animal 

 corpuscles. Moreover, from human anti-B immune rabbit serum only B of 

 human origin and B from some anthropoid apes can absorb the B agglutinin ; 

 whereas the B corpuscles from other animal species cannot do so. Further 

 investigations made it then very probable that the agglutinogens A and B 

 can be subdivided into various fractions and that, correspondingly, the dif- 

 ferent serum agglutinins can be subdivided ; also, that certain of these second- 

 ary differentials may be common to human blood and that of various animal 

 species, while others are peculiar to single species. The question now arises 

 as to how far it is possible to proceed with this process of subdividing cor- 

 puscles and sera; it is not improbable that by increasing the number of tests 

 between corpuscles and sera of man and those of different types of immune 

 sera against a greater variety of blood corpuscles, employing other species 

 than the rabbit as donor of the immune sera, the number of subdivisions 

 may be still further augmented. In addition the question suggests itself as to 

 whether experiments of this type actually prove the existence of multiple 

 differentials and agglutinins, or whether we have to deal merely with quantita- 

 tive differences in the strength of different differentials and agglutinins and 

 with the presence of substances which may interfere with the absorption 

 processes in different types of blood. 



We have seen, then, that various species of animals, including the human 

 species, have certain differentials in common, without regard to the relation- 

 ship of these species. In addition, a connection has been established between 

 blood-group differentials and differentials of different kinds. Thus a relation 

 has been noted between the human blood-group differential A and the 

 Forssman differential of sheep erythrocytes, guinea pig kidney, and certain 

 cells of other heterogenetic species, and even of some bacteria. Schiff and 

 Adelsberger first found that through immunization of rabbits with human 

 erythrocytes A, hemolysins for sheep corpuscles are produced, as well as im- 

 mune agglutinins for the human corpuscles of Group A. As to whether dif- 

 ferential A and the Forssman differential are identical, or whether they occur 

 side by side in the same human corpuscles, it seems, according to investiga- 

 tions of Sachs and Witebsky, that the second alternative holds good. It can 

 be shown that some sheep corpuscles which possess Forssman antigen — as 

 well as other sheep corpuscles which do not possess it — have no human A 



