DEMONSTRATION OF INDIVIDUALITY DIFFERENTIALS 513 



consider the possibility that in the corpuscles of the calf the antigens were 

 quantitatively not yet as fully developed as in the corpuscles of the mother. 

 Examination of a family of sheep, consisting of father, mother and three 

 lambs, showed that the corpuscles of one lamb behaved in an almost identical 

 manner with those of the mother, while the corpuscles of the other two lambs 

 had the character of the father. Here, too, there is a lack of gradation, and 

 there is again reason for assuming that under similar conditions transplanta- 

 tion would in all probability have revealed graded differences between the 

 constitution of the cells of the various children and of father and mother. An- 

 other peculiarity in these experiments needs particular mention, namely, the 

 importance of the race to which the individual cattle belonged. We should have 

 expected the erythrocytes of a certain individual to resemble more the cor- 

 puscles of an individual belonging to the same strain than the corpuscles of 

 an individual from a different strain, but this was apparently not the case. In 

 transplantation experiments, on the other hand, the differences existing be- 

 tween different strains, such as white, yellow and piebald strains of rats, and 

 also those between inbred strains of guinea pigs and mice, have a distinct 

 effect on the reaction of the host against the grafts. 



In more recent experiments Todd analyzed in a similar manner, individual 

 relationships in fowl by means of immune hemagglutinins. Here, too, it was 

 found that by absorption tests the red corpuscles of each individual animal 

 could be distinguished from those of others. Some erythrocytes resembled 

 each other more than others ; but certain members of the family could not 

 be distinguished from one another by this method. In these experiments poly- 

 valent sera were used. If they were absorbed with the corpuscles of one 

 individual, only immune substances directed against this individual and 

 against some near relatives were thereby removed ; but if the polyvalent serum 

 was exhausted with the red corpuscles of several individuals, the number of 

 immune substances removed was greater. Also, in this case we find a lack 

 of a furthergoing gradation in the relationship of the various individuals. In 

 analyzing the relationship between parents and children, Todd found, again, 

 the corpuscles of some children behaving like those of the father, others like 

 those of the mother; but in two instances the antigens of the children pos- 

 sessed components of both father and mother. If a polyvalent serum is ab- 

 sorbed with the erythrocytes of both parents successively, it has of course, 

 lost also the agglutinins for the cells of the child completely. Theoretically, 

 the red corpuscles of the child should have components of the parents to an 

 unequal degree in the large majority of cases. This is found in transplanta- 

 tion experiments and they suggest that there does not, as a rule, exist an 

 identity between the structure of the differentials of a child and of one of the 

 parents. 



An indication that it is perhaps the differentials which serve to distinguish 

 the erythrocytes of various individuals, and that they also function as antigens 

 in immunization, was obtained in experiments in which the production of 

 agglutinins against the blood corpuscles of brothers and sisters was tested. In 

 each instance, Todd injected a chicken with the blood of a brother. Several 



