518 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



nature, not normally circulating in the bodyfluids, may call forth the produc- 

 tion of immune substances if they gain access to the circulation. 



It may then be concluded that in the erythrocytes of several species the 

 presence of differentials of an individual character has been established by 

 means of immune sera, but it has not yet been definitely proved that these 

 differentials are identical with the individuality differentials. Even in some 

 preformed sera, such as ox serum, multiple agglutinins seem to exist, which 

 can be specifically absorbed by the erythrocytes of certain individuals. This 

 fact may be interpreted as indicating that complexities in the structure of 

 blood proteins exist, which have not yet been amenable to a purely chemical 

 analysis. 



