152 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



rabbit, and by testing erythrocytes of various cattle with the normal sera of 

 individuals from different species, a considerable number of additional anti- 

 gens may be found in cattle erythrocytes. There is therefore no basis for the 

 suggestion made by these authors that each one of the thirty genes, corre- 

 sponding to the thirty antigenic substances found so far, might be located in 

 one of the thirty chromosome pairs which the cells of cattle are supposed to 

 possess. Inasmuch as these antigenic (individuality differential) substances 

 are genetically determined, it is to be assumed that, considering the relatively 

 large number of these substances, on the average there should be a greater 

 similarity between the sets present in parents and offspring than between the 

 sets of less closely related individuals. Experiments were in agreement with 

 this postulate. And there is thus, in this respect, a correspondence between the 

 effects of these multiple factors present in erythrocytes and the individuality 

 differentials of tissues in general. 



In the meantime, Landsteiner and others, by studying further the agglutina- 

 tion reactions in blood of man and of other species, had added several addi- 

 tional factors (P.M.N., Rh., A x and A 2 ) to the original A and B which were 

 found in erythrocytes; accordingly, the number of factors which have to be 

 considered in selecting compatible donors and receivers in transfusions of 

 blood has also increased, and it seems very probable that this number will be 

 still further increased in the future. As to the different agglutinogens which 

 are present in and distinguish the red corpuscles of fowl, Kozelka, who also 

 extended the work of Todd, believes it possible that their number is small, 

 notwithstanding the infinite number of individuals which all differ in the 

 character of their erythrocytes. This opinion is based on the fact to which 

 Landsteiner and Wiener have repeatedly drawn attention, namely, that there 

 are a great many possible combinations of relatively few factors. On the other 

 hand, it must also be remembered that the greater the number is of different 

 rabbit immune sera and of natural sera from different species which are used 

 for testing the agglutination and hemolysis of the corpuscles of individual 

 fowl or mammals, the greater will become the number of factors which dis- 

 tinguish the erythrocytes of individual organisms. While it is true that the- 

 oretically a limited number of factors would suffice to account for a large 

 number of differences between different individuals of a certain species, this 

 does not necessarily prove that the number is actually very small. 



As far as the individuality differentials are concerned, there are strong 

 indications that the number of distinguishing factors is very great. We have 

 referred already to some experimental data which strongly support this con- 

 clusion, such as the many fine gradations found in the strength of the reac- 

 tions against syngenesious and homoiogenous tissues, in accordance with the 

 relationship of donor and host, and the fact that no autogenous reaction is 

 found against homoiogenous or syngenesious tissues except when we weaken 

 artificially the ability of the host to attack the strange transplant, but that 

 autogenous reactions occur only if the host and transplant possess the same 

 genetic constitution. Furthermore, marked differences between the individu- 

 ality differentials of host and graft lead to rapid and strong reactions, and 



