256 PASSIVE IMMUNIZATION 



streptococci by means of a corresponding antiserum had been shown 

 by v. Behring himself in 1892, and shortly after a number of French 

 observers attempted to influence the infection in the human being 

 also in a similar manner. 



The most noteworthy of these early attempts is intimately con- 

 nected with the name of Marmoreck. This investigator, believing 

 in the unity of practically all the different types of streptococci 

 which are pathogenic for man, succeeded in increasing the virulence 

 of an angina strain by animal passage to such a degree that 

 0.000000001 c.c. was sufficient to kill a rabbit with acute symptoms. 

 With this strain he immunized horses and sheep and then recom- 

 mended the resulting antiserum, which is thus a monovalent serum, 

 for the treatment of all forms of streptococcus infections occurring 

 in the human being. The results, however, were practically nil. 



If we come to investigate the reasons which may be responsible 

 for this want of action, different possibilities suggest themselves. 

 On the one hand, it is conceivable that the identity of the different 

 strains is only apparent and that Marmoreck's serum was inactive 

 merely because it was monovalent, i. e., because it had been produced 

 with but a single strain. If this were so it would evidently be neces- 

 sary to prepare a polyvalent antiserum, i. e., to immunize animals 

 with as many different strains as possible, and to use the resultant 

 product. Or, one might imagine that in consequence of animal 

 passage, to increase the virulence of a different strain, the organism 

 could become so altered in its biological properties that its virulence 

 for the human being would be diminished or lost, and that the 

 corresponding antiserum, though active for the animals through 

 which the passage had been conducted, might still be inactive in 

 the human being. In such an event, animal passage would have to 

 be omitted, and a monovalent or polyvalent serum prepared by 

 immunizing directly with strains that had been obtained from human 

 beings (sc., with cultures made from human sources only). 



Both possibilities have indeed been considered and practically 

 tested. Denys and Van der Velde thus prepared a polyvalent 

 serum from a number of different strains, whose virulence had been 

 further increased by animal passage, but this serum also has fallen 

 into oblivion, which suggests that subsequent investigations did not 

 support the favorable reports which first followed its introduction. 

 Tavel, Krumbein, and Paltauf, on the other hand, prepared polyv- 



