CHAPTER XVIII. 



PASSIVE IMMUNIZATION (SERUM THERAPY). BACTERIOLYTIC SERA. 

 SPECIAL SERUM THERAPY. 



In the former chapters it was proven that during active immunization 

 of an animal specific protective bodies were formed which circulate in the 

 blood and can by means of the serum be transferred to another organism. 

 It was further found that such bodies exert this protection against fatal 

 intoxication or infection in various ways; thus, as antitoxins and anti- 

 aggressins they neutralize toxic poisons and aggressins; as bacteriolysins 

 they bring about lysis of the bacteria; while as bacteriotropins they prepare 

 the bacteria for phagocytosis. The defensive qualities of such a transferred 

 serum are evident not only if the infection is incited at the same time as, or 

 a short period after the serum is given, but in numerous instances curative 

 effects are observed if the serum is given even after infection has already 

 taken place. 



Of all sera, those with antitoxic properties have met the greatest suc- 

 cess in therapeutic application. They have already been referred to in 

 their respective chapters. 



The efficiency of the pure bacteriolytic sera on the other hand has been dis- 

 appointing. One reason given for this lack of curative action is, the in- 

 ability of bacteriolytic serum to neutralize the endotoxins. 



Pfeiffer's experiment revealed that if the number of bacteria exceeded a certain 

 limit, then in spite of bacteriolysis, death of the animal takes place. This was explained 

 by the existence of endotoxins. By bacteriolysis the endotoxins normally confined 

 within the bacteria are liberated and thus get a chance to show their toxicity. 



The aim, therefore, was to produce antiendotoxic sera. The accomplishment of 

 this was prevented by the erroneous view of Wolff-Eisner who claimed that it was 

 impossible to immunize against endotoxin. 



Numerous methods have been advocated for the liberation of these endotoxins: 

 maceration of bacteria, exposure to very low temperature, admixture with chemical 

 substances which would dissolve the outer capsule, ferment digestion, growth upon 

 certain culture media, etc. At the present day, there is absolutely no doubt that the 

 bacterial bodies contain poisonous substances against which it is difficult and to a cer- 

 tain degree impossible to attain an immunity. 



Whether one should adhere to the old idea and apply to these the term endotoxin, 

 or include them in the class of true toxins with the only difference that they are not 

 secreted but contained within the bacterial body and therefore more difficult to isolate, 

 is purely a question of theoretical importance. 



Another cause for the therapeutic failure of bacteriolytic serum, as ad- 



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