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ANTITOXINS 



to those produced by tetanus and diphtheria. Potent toxins are sel- 

 dom secured with less than two to three weeks' incubation, and fresh 

 cultures of whole or autolyzed bacilli are likewise quite too toxic, in- 

 dicating that although a soluble toxin may be produced, considerable 

 endotoxin is also present in the bacilli. 



Antidysenteric serum has very little prophylactic value, but in in- 

 dividual cases it frequently exerts a curative action, and should be 

 available for use in institutions and armies when dysenteric infection 

 is prevalent. 



The older investigators, such as Kruse and Shiga, produced anti- 

 serums by immunization with whole bacilli. Later Kraus and Doerr 

 prepared antitoxic serums with the toxin alone. At the present time 

 the evidence would seem to indicate that the best serums are prepared 

 by injecting both toxins and bacilli, producing a serum that is essen- 

 tially antitoxic and bactericidal in action. 



Culture. Young and healthy horses are best adapted for immuniza- 

 tion. Two methods may be followed: (1) Immunization with toxin 

 or (2) with young cultures of whole bacilli. As previously mentioned, 

 investigations have tended to show that the most potent serums are 

 secured by using mixtures of both toxin and microorganisms. 



Several strains of dysentery bacilli should be used, in order that a 

 polyvalent serum may be prepared. Cultures should be grown for two 

 weeks at 37 C., in alkaline broth similar to that used for preparing diph- 

 theria toxin; this should be neutralized to phenolphthalein, and 7 c.c. 

 normal soda solution to a liter added. The minimal lethal dose of the 

 mixed unfiltered cultures is determined by giving young rabbits increas- 

 ing doses intravenously, in order to obtain a guide as to the proper dose 

 for immunization. Fatal doses produce severe diarrhea and paralysis 

 of the extremities, with rapid loss in weight. Rabbits and horses are 

 quite susceptible to the toxin; guinea-pigs and mice are more resistant. 



TABLE 3. METHOD OF DETERMINING THE MINIMAL LETHAL DOSE 

 OF DYSENTERY CULTURE 



