230 GENERAL THERAPEUTICS FOR VETERINARIANS 



5. According to Much (Immunitatswissenschaft, 1911), a distinction 

 must be made between toxin bacteria and endotoxin bacteria in considering 

 the immunizing processes occurring in the different infectious diseases. 



I. The toxin bacteria remain at the point of infection (tetanus, diph- 

 theria, sausage poisoning) and act pathogenically by the excretion of poisons 

 (bacterial poisons or toxins). The antitoxins are the antidotes, which appear 

 in the blood-serum in consequence of the presence of the toxins. The anti- 

 toxic serum acts against the toxins as well as against the bacteria. 



II. The endotoxin bacteria spread through the body (septicaemia, strepto- 

 cocci) and exert a pathogenic effect not only through the toxins excreted but 

 also through the cell substances of the bacteria (endotoxins) when they dis- 

 integrate in the animal body. They are not counteracted by antitoxins, but 

 the substances which protect the body against these organisms are: 1, normal 

 humoral bacteriocidins, i.e., the bactericidal substances which are present in 

 solution in every normal serum (serum substances); 2, normal leucocytic 

 bacteriocidins, i.e., the bactericidal substances in solution which originate 

 from the leucocytes (plasma substances) ; 3, specific humoral bacteriocidins, 

 which appear in the serum in the later stages of the infection — these three 

 protective substances destroy the hving organisms; 4, the poisonous substances 

 of the endobacteria, the endotoxins, are destroyed through phagocytosis by 

 the leucocytes, while phagocytosis is again stimulated by the bacteriocidins. 



The Weakening (Mitigation) or Attenuation of the Infec- 

 tious Materials. — In every protective or curative vaccination it 

 is important that the infectious material be used in a weakened, 

 mild (mitigated), diluted (attenuated) form, since the unweak- 

 ened, unattenuated virus will produce a severe or fatal infection. 

 The methods and manner of attenuation are very different. The 

 most important, arranged in historical order, are the following: 



1. The introduction of a small quantity of the infectious 

 material. The greater the number of a pathogenic organism in 

 the body the more pronounced the effect; therefore, in vaccination 

 care must be exercised that only a minimum quantity of the 

 infectious material is inoculated, otherwise the original disease 

 will be produced in undiminished strength. 



2. The selection of a different entrance point for the infec- 

 tious material. Under ordinary conditions the contagion of most 

 infections is taken in through the internal organs, especially the 

 respiratory and digestive apparatus. This has been demonstrated 



