548 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



as, for instance, those directed against leucocytes, brain or carcinoma; on 

 the other hand, they serve as organ-specific antigens in combination with 

 heterogenous sera functioning as carriers, as has been shown in the case of 

 lens and brain. 



As far as the immune serum against leucocytes is concerned, the reaction 

 with the organ-specific component of these cells seems to be intensified if the 

 alcohol soluble fraction is used as antigen, but the species-specific constituent 

 is also present in this alcohol soluble fraction. Still more pronounced organ- 

 specific effects can be obtained, according to Witebsky, if boiled suspensions of 

 leucocytes serve as antigens. In such immune sera the organ-specific com- 

 ponent predominates decidedly over the organismal-specific component, which 

 latter may be lacking altogether. Likewise, through heating of thyreoglobulins 

 the species-specific differential can be destroyed, while the substance- and 

 organ-specific component remains preserved. In some instances the alcohol 

 soluble organ differentials were found to be the more specific ones. 



We may then conclude that organ or substance specificity may be associated 

 with an active protein, or with a different substance which in combination 

 with a protein serves as antigen. In the case of thyreoglobulin or other organ 

 globulins, the organ specificity is presumably due to a sidechain attached to 

 a protein. This sidechain may act similarly to the radicles introduced into 

 complex proteins, or, in general, into complex colloidal substances in the 

 experiments of Obermayer and Pick, and of Landsteiner and his collabora- 

 tors. Graded reactions between different organs may perhaps depend upon a 

 multiplicity of differential substances, some of which may be common to 

 them while others are distinctive for certain of these organs. On the other 

 hand, the organismal differentials are native proteins and they are therefore 

 destroyed by heating, in contrast with the organ differentials, which are not 

 destroyed by this procedure. There is however, some evidence that in some 

 organismal differentials an alcohol soluble component may be present; in this 

 case we may have to deal with the secondary or accessory type of organismal 

 differentials. 



Absorption experiments have shown that after immunization with appar- 

 ently single substances, such as fibrinogen and thyreoglobulin, antibodies 

 develop not only against the fibrinogen and thyreoglobulin of the species 

 which served as antigen — these represent the principal antibodies — but also 

 against the corresponding substances of related species; these would be 

 associated antibodies. Now it is possible, as especially Hektoen and his col- 

 laborators have shown, to remove all the antibodies against certain substances, 

 the principal as well as the associated ones, by absorption with the antigen 

 from the original species, while only the associated, but not the principal, 

 antibodies are removed by absorption with the differential substance derived 

 from related species. Similar observations have been made by various investi- 

 gators also in the case of other antigens and antibodies. Here apparently 

 are involved single substances calling forth the production of antibodies, and 

 we must therefore assume that in the molecules of these substances graded 

 differences exist in different species, which correspond to the relationship of 



