DEMONSTRATION OF INDIVIDUALITY DIFFERENTIALS 511 



which are obtained in the analysis of individuality differentials by means of 

 transplantation, the reaction depending here not merely on the nature of the 

 transplant, but on the relation between the individuality differential of the 

 donor and of the host. While it was thus possible to produce substances which 

 Ehrlich and Morgenroth called "isolysins" — but which would, perhaps, better 

 be called "homoiolysins" — in no case did such a homoiohemolysin dissolve the 

 erythrocytes of the animal which had produced that particular hemolysin. 

 Autohemolysins did not develop under these conditions. However, in some 

 goats it was not possible to elicit the production of homoiohemolysins in this 

 way; here the injected homoiogenous red corpuscles behaved like autogenous 

 cells. Another difficulty was that the antisera not only reacted with the red 

 corpuscles of the goat which had furnished the antigen, but also with the 

 erythrocytes of a number of other goats. These facts suggested to von Dun- 

 gern and Hirschfeld, as well as to Witebsky, the interpretation that Ehrlich 

 and Morgenroth had in reality not to deal with individual hemolysins, but with 

 group isolysins corresponding to the group hemagglutinins, the occurrence of 

 which in certain animal species had been demonstrated by von Dungern and 

 Hirschfeld. Also, Zinsser assumed that while Ehrlich and Morgenroth had 

 actually discovered individual differences, between the red corpuscles of differ- 

 ent goats, these individual differences were identical with blood-group differ- 

 ences. 



As discussed previously, it is necessary to distinguish between at least four 

 different kinds of substances: (1) The typical group differentials, which are 

 represented in man by the agglutinogens A and B; (2) accessory blood-group 

 differentials, such as M, N, P, Rh and H; (3) substances which allow the 

 distinction of individuals, as for instance, individual scents, and also certain 

 tissue or organ differentials, or combinations of the latter. While a combina- 

 tion of a sufficiently large number of accessory blood-group or organ differen- 

 tials might permit the distinction between individuals, this would not make 

 these individual differences necessarily identical with (4) the individuality 

 differentials. It is difficult to determine whether Ehrlich and Morgenroth had 

 to deal with substances enumerated under 2, 3, or 4. 



However this may be, the desire of Ehrlich and Morgenroth to determine 

 the possibility of the formation of "isohemolysins" suggested to them the 

 use of a method which allowed a much finer differentiation between in- 

 dividuals than had been possible previously by means of serological methods, 

 in particular, those in which the ordinary heterogenous immune sera were 

 employed. These investigators anticipated the essential feature of the method 

 of cross immunization, subsequently introduced by Uhlenhuth with a view 

 of refining the precipitin test. Furthermore, the use of cells instead of blood 

 proteins as antigens may have been a favorable factor which made possible 

 the demonstration of individual differences by serological methods. 



The fact that homoio (iso) hemolysins can be produced experimentally was 

 subsequently confirmed by Ascoli and by various other investigators. But the 

 most extensive and important studies concerning the demonstration of in- 

 dividual differences between the red blood corpuscles of different individuals, 



