574 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



between the organismal differential (antigen) of a certain species and the 

 various antibodies present in the immune serum; the pattern of the protein 

 corresponding to the order in which certain amino-acid radicles recur in the 

 molecule may perhaps be a factor which helps to determine the character of 

 the antibody. This view agrees also with the views recently expressed by 

 Landsteiner and with the observations of the latter that the specificity of 

 immune sera for polypeptides may depend upon a pentapeptide in its entirety. 

 Therefore, large groups and their specific pattern of amino acids may deter- 

 mine phylogenetic relationship. On the other hand, in contrast to the organis- 

 mal differentials, the specificity of other antigens such as the various ag- 

 glutinogens which determine the specific blood-group reactions and which 

 seem to be complex nitrogen-containing carbohydrates, may be quite distinct 

 from each other and not show multiple intermediate substances. Here the 

 differences between the various antigens can be conceived as of a more abrupt 

 nature and perhaps due to single groups sharply differentiated from those 

 of other analogous antigens. 



While there can be no doubt that it is the proteins which primarily 

 determine the specificity of the organismal differentials, there are some 

 serological experiments which indicate that in certain cases also some other 

 hapten-like substances may perhaps be concerned in similar reactions. Thus, 

 it has been observed that while whole erythrocytes are required in order to 

 produce species-specific antisera for the red corpuscles of certain species, 

 alcohol extracts of the same kind of red corpuscles may react specifically 

 with such immune sera ; it appears therefore that in this case the antigen 

 contains an alcohol soluble hapten, and as Landsteiner has shown, the 

 hemolytic action of such species-spectific hemolysins may be inhibited by 

 addition of ether extracts of such red corpuscles to the antibody. These 

 observations would agree with the finding made in the course of our trans- 

 plantations of tissues and previously discussed, that the species differentials 

 differ from the individuality differentials in that the former are somewhat 

 less heat sensitive than the latter. These complex species differentials present 

 in erythrocytes could resemble the organ differentials which withstand boiling 

 in contrast to the typical species differentials which are destroyed by boiling; 

 the organ, tissue or substance specificity may perhaps reside in the hapten, 

 while the typical species specificity resides presumably in the protein with 

 which the hapten is associated. In these particular substances the species- 

 specific component of the antigen may then perhaps consist of a hapten of a 

 non-protein nature. An important point to be considered in this connection 

 is the fact that the presence of a chemical factor, graded as to phylogenetic 

 relationship of the animal group and characteristic of the typical organismal 

 differentials, has apparently not been demonstrated in these antigens or in 

 parts of the antigens contained in the alcohol extracts. 



It might therefore perhaps be necessary to distinguish between the primary 

 species differentials of protein nature, and secondary complex differentials 

 which represent combinations of organ or "substance" differentials and the 

 species differentials, an interpretation which we have mentioned in previous 



