AGGRESSIN. 193 



Another cause for the therapeutic failure of bacteriolytk serum, is given 

 by Bail and his school, as the lack of its antiaggressin action. This applies 

 only to the cases in which the bacteriolytic serum was produced by immuniza- 

 tion with dead bacteria. 



When live bacteria are used, this objection is not to be considered, as 

 according to the experiments of Wassermann and Citron, "aggressin" is 

 nothing more than the immunizing substance of the living bacteria. As for 

 the structure of the antiaggressins, the author was able to show that like the 

 bacteriolysins, they are amboceptors which bind complement. 



Artificial aqueous extracts of living bacteria belonging to the class of 

 half parasites made according to the method of Wassermann and Citron, 

 contain the endotoxin as well as the aggressin. Such artificial aggressins, 

 therefore, represent ideal antigens. The sera produced by their injection 

 contain but few bacteriolytic bodies and a very large number of amboceptors, 

 easily demonstrable by the Bordet-Gengou reaction. 



Wassermann explains the lack of therapeutic efficiency on the part of the 

 bacteriolytic sera, by the absence of complement of the organism, as well as 

 by the inability of human complement to fit all animal amboceptors. As is 

 known, amboceptors increase during immunization while the complement 

 content remains the same. But since amboceptors without complement 

 remain inactive, even a very strong serum may only be slightly effective, 

 depending upon the amount of existing complement. If too many ambo- 

 ceptors are injected, the serum may become entirely powerless due to a 

 phenomenon similar to Neisser and Wechsberg's complement deviation. 

 Wassermann advises therefore the addition of complement to a serum 

 before its injection, in order to activate it. This suggestion has not been 

 widely adopted in practice. 



It is for a similar reason, that the classical experiment of bacteriolysis 

 is so beautifully demonstrable in the guinea-pig's peritoneal cavity, an 

 area relatively poor in cells, while this phenomenon is incomplete and 

 replaced by phagocytosis when occurring in the blood, inner organs, and sub- 

 cutaneous connective tissue. It is in this connection that Metschnikoff and 

 his followers see the main reason for the failure of the therapeutic activity 

 of bacteriolytic sera. 



An additional impediment is offered by the wide differences which exist 

 between the numerous strains of the same bacterium. This may be so 

 marked that an immune serum produced with one strain will enfold no pro- 

 tection against a different strain of the same bacterium. It is now overcome 

 to a certain extent by immunization with as many different strains of the 

 same bacterium as possible (polyvalent sera). 



Cultures grown upon artificial media for a very long time, adapt them- 

 selves entirely to their new surroundings and frequently lose some of their 

 biological characteristics, e.g., virulence. If the culture is then inoculated 

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