BLOOD GROUPS, HETEROGENETIC ANTIGENS 489 



of this substance may pass from the organs into the serum. In those rabbits 

 which contain the A differential, the anti-A agglutinin is lacking in the serum ; 

 on the other hand, the anti-A agglutinin can be demonstrated in the serum of 

 those individuals in which the A differential is not present in their organs 

 (W. Treibman). The latter type of animals can be immunized against the 

 human A differential, which is strange to them ; while the former type, which 

 possesses the differential, cannot thus be immunized. These observations 

 indicate very strongly that the A differential occurring in the organs and 

 serum of certain individual rabbits, is essentially the same as that occurring in 

 the erythrocytes of man. 



In a corresponding manner, according to Hirszfeld and Halber (1928), the 

 isoagglutinable substance of sheep and hog is serologically identical with the 

 isoagglutinable substance A of human blood. The isoagglutinable blood cor- 

 puscles of certain sheep and hogs absorb all the anti-serum A antibodies 

 obtained through immunization, whereas the non-agglutinable blood cor- 

 puscles of other sheep and hogs do not possess this property. Therefore, ac- 

 cording to these investigators, we must conclude that sheep and hogs actually 

 possess an A differential identical with that of man. 



Still, certain differences seem to exist between the A differential in human 

 corpuscles of blood-group II and in those sheep corpuscles which also possess 

 A. While by means of absorption with A-containing sheep corpuscles it is 

 possible to absorb more antibodies from the serum of rabbits immunized 

 against the human A differential, than by using for this purpose sheep cor- 

 puscles which do not contain the A differential, on the other hand, if the 

 sera of rabbits immunized against A-containing sheep corpuscles are absorbed 

 with A sheep corpuscles, then all antibodies against the A differential of 

 sheep corpuscles are entirely removed, but only a part of the antibodies against 

 human corpuscles of group A is removed. Similarly, from serum of rabbits 

 immunized against human differential A, the antibody against the A differen- 

 tial of sheep corpuscles can be entirely removed through absorption with 

 sheep corpuscles containing A, but there remains, then, still a reaction against 

 an alcohol extract from human A corpuscles. These observations have led to 

 the conclusion that there exists not a complete, but only a partial identity 

 between the A differential in the erythrocytes of man and of sheep; but we 

 may possibly have to deal merely with quantitative differences between the 

 A differential as it occurs in man and in certain animal species. 



While no isoagglutinable substance was found by direct test in Polish 

 cattle, indirectly a grouping could be demonstrated in these cattle erythrocytes. 

 Cattle and sheep corpuscles have a receptor in common, as is shown by the 

 fact that the amboceptor in the serum of rabbits immunized against sheep 

 corpuscles hemolyzes not only sheep but also cattle corpuscles, whereas the 

 anti-Forssman serum, obtained through injection of guinea pig kidney into 

 rabbit, which also hemolyzes sheep corpuscles, does not affect cattle corpuscles. 

 Therefore the antigen in sheep corpuscles which gives rise to the formation 

 of antibodies able to act on certain cattle corpuscles, is not identical with the 



