570 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



diazotized atoxyl with the animal's own serum may serve as antigen. We 

 have discussed this problem in a preceding chapter. However, while foreign 

 sera seem to fulfill the function of carriers of the haptens efficiently, 

 Armangue, Gonzales and Morata have shown that the Forssman differential, 

 which by itself is not at all or only very slightly antigenic, can be converted 

 into an active antigen also by mixing it with kaolin or other absorbent 

 substances instead of with serum. Zogaya has found that a complex bacterial 

 polysaccharide may serve as a satisfactory antigen if it is first absorbed by 

 collodion or carbon particles. Landsteiner and Jacobs confirmed these obser- 

 vations, but they also noted that purified bacterial polysaccharides or other 

 complex carbohydrates, when freed as much as possible from N-containing 

 substances, can no longer be activated by these non-specific, absorbent colloids, 

 and the same applies to the purified Forssman differential. It seems, then, 

 that certain impurities which are mixed with the differentials may somehow 

 enhance their antigenic power, and this process can be still further accen- 

 tuated by combination with absorbent colloids. 



It has been noted by Goebel and Avery that also some glucosides in com- 

 bination with heterogenous proteins may act as haptens; in this case, 

 stereoisomeric differences may help to determine specificity and, therefore, 

 the substitution of a galactose for the glucose radicle in the glucoside may 

 lead to a new specificity. The stereoisomeric differences in the galactose and 

 glucose group resulted in the formation of specific antibodies. It is of interest 

 in this connection that while in the composite antigen the glucoside and 

 protein are combined into one substance, two separate antibodies seem to 

 develop in response to the injection of this antigen, and these are apparently 

 distinct from each other; moreover, it was found possible to remove the 

 one by specific absorption without at the same time removing the other. The 

 glucoside as such, acting as hapten, inhibited only the interaction of the 

 anti-carbohydrate antibody and not that of the anti-protein antibody with the 

 antigen. In general, it may be stated that, in accordance with the findings of 

 Landsteiner, a simple antigen, in which the chemical constitution of the hapten 

 is well known, may cause the production of several distinct antibodies, which 

 are directed against different groups in these antigens and which can be 

 removed by specific absorption. Or the antibody may represent, perhaps, a 

 very complex composite structure, in which different groups combine with 

 different component parts of the antigens chemically, with different degrees 

 of firmness ; and conversely, there may be different degrees of dissociation 

 between the constituents in the antigen and antibody combination. In this way 

 Heidelberger interpreted the occurrence of various kinds of cross-reactions 

 between antisera and antigens. 



Goebel in more recent investigations analyzed still further the conditions 

 which cause the specificity of antigens by the use of artificial antigens against 

 various types of pneumococci. One of these antigens contained the azobenzol 

 glucoside of glucuronic acid, the other, that of galacturonic acid. The differ- 

 ence in stereoisomeric constitution of these two glucosides has a marked 

 influence on the serological specificity of these two antigens. The immune 



