512 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



belonging to the same species, were carried out by Todd and White, and later 

 by Todd alone. We have referred already to their work and we shall now 

 again discuss these investigations. There can be little doubt that these latter 

 investigators had to deal with individual and not with group differentials in 

 their investigations. Todd and White, and Todd, in preparing immune serum 

 against cattle plague, injected different cattle with the blood of other cattle. 

 Out of one hundred and six cattle injected, seventy-six furnished active sera 

 containing homoio (iso) hemolysins for normal cattle, which were active in 

 combination with guinea pig complement. Each immune serum thus obtained 

 was able to hemolyze the red corpuscles of certain other individual cattle, and 

 this action differed from that of the immune serum obtained from another 

 animal. Thus a particular serum was very hemolytic for some kinds of 

 erythrocytes and only weakly hemolytic for others, and each serum acted 

 in its own specific way on the various kinds of corpuscles. The order in which 

 two different sera affected a series of corpuscles from different individuals was 

 different in each case. 



These individual variations between the antigens present in the corpuscles 

 of different cattle were brought out still more strikingly in specific absorption 

 experiments. If a certain serum was exhausted by the addition of the red 

 corpuscles of an individual animal, it lost thereby not only the ability to 

 hemolyze the kind of corpuscles which had been used for absorption, but 

 also the erythrocytes of some other individuals ; moreover, a gradation be- 

 tween the erythrocytes of different individuals according to genetic relation- 

 ship, such as had been observed in transplantation experiments, did not ap- 

 parently exist here; it seemed, rather, that "an all or nothing" law obtained. 

 But if several immune sera were pooled, the absorption tests became more 

 specific, in so far as now absorption with the corpuscles of one particular 

 animal removed, primarily, the hemolysins of this individual, leaving the 

 others as a rule intact. Still it might happen here also, that not only the 

 hemolysins for those individuals whose corpuscles were used for specific 

 absorption were removed, but also the hemolysins for some other individuals. 

 It appears that if the relationship between two individuals did not exceed 

 a certain degree of remoteness, their erythrocytes behaved alike in the ab- 

 sorption test, a finer quantitative gradation in the intensity of the reaction, 

 such as can readily be accomplished by means of transplantation, being im- 

 possible in this case. However, in an indirect manner, by comparing the be- 

 havior of the corpuscles of various individuals to different immune sera it 

 might perhaps have been possible to establish the mutual relationship of the 

 corpuscles of the various individual cattle, at least in an approximate manner. 



The same lack of gradation was also apparent in the analysis of the relation- 

 ships of the members of certain families by means of the hemolysis test. Thus 

 the blood corpuscles of a cow and her calf were compared as to their specific 

 ability to absorb the individual hemolysins. It was found that absorption with 

 the corpuscles of the mother removed also the hemolysins for the calf, but 

 absorption with the corpuscles of the calf left the hemolysins of the mother 

 intact, while removing those for its own corpuscles. In this case we have to 



