506 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



in the sera of the immunized organism the presence of immune substances 

 which react specifically with the antigens used for their production, but which 

 also react more weakly with analogous substances from related species in a 

 graded manner, in accordance with the graded relationships of the various 

 species. How do preformed agglutinins and hemolysins behave in this respect ? 

 Do they show the same degree of specificity as do the immune substances? 

 There are present in the sera preformed antibodies which react with group 

 antigens in the erythrocytes. The question now arises whether there exists a 

 specific adaptation between preformed antibodies in sera, on the one hand, 

 and erythrocytes and other cells, on the other, in accordance with the system- 

 atic relationship of the organisms from which the sera and cells are derived. 

 Such a specific adaptation would be comparable to that which obtains be- 

 tween constituents of the plasma and tissue coagulins, and which becomes 

 manifest in the coagulation of the blood. We have already discussed the fact 

 that a specifically graded relationship between blood sera and erythrocytes of 

 various species, corresponding to the phylogenetic relationship, has not yet 

 been demonstrated by means of hemagglutination. Marshall likewise found 

 that normal heterogenous sera of goat, sheep, goose, or rabbit were equally 

 hemolytic for human and Macacus blood. Landsteiner observed that normal 

 hemagglutinins absorbed by certain erythrocytes and then dissociated from 

 this combination by elution, are active with the red corpuscles from numerous 

 near and distant species. Thus solutions of agglutinin obtained by washing 

 rabbit erythrocytes, which had previously been agglutinated by beef serum, 

 acted intensely with both rabbit and frog erythrocytes. Landsteiner concluded 

 therefore that agglutination or failure of agglutination of erythrocytes by the 

 normal serum of another species is almost independent of the systematic re- 

 lationship of those species. As far as agglutination of erythrocytes is con- 

 cerned, this lack of agreement is understandable, since within the same species 

 corpuscles from different individuals differ from each other as regards their 

 agglutinability by the sera of other individuals of the same species, and since 

 not only agglutinins exist in the sera of various species which agglutinate 

 human red corpuscles, but heterogenous sera in general may agglutinate 

 corpuscles from other species, irrespective of systematic relationship. Like- 

 wise, the presence of Forssman differentials and of other antigens of a similar 

 kind, which, as we have seen, do not conform to the laws of systematic re- 

 lationship, may interfere with and prevent a parallelism between the reactions 

 of sera on cells of a heterogenous nature and the systematic relationship of 

 the various species, genera, orders and classes of animals from which the 

 sera and cells are derived. Thus, according to Klopstock and Lehmann- 

 Facius, the sera of species possessing Forssman antigens dissolve cells of 

 various species, irrespective of whether they belong to the heterogenetic or 

 the non-heterogenetic series ; on the other hand, sera from non-heterogenetic 

 species dissolve only cells from heterogenetic species. But in addition, another 

 factor may interfere with the manifestation of a parallelism between the 

 toxicity of heterogenous sera and the systematic relationship of two species. 

 There seem to occur in the same serum multiple constituents, each one directed 



