Immunity 587 



such as pneumonia, endocarditis, etc. Horder* has culti- 

 vated it from the valvular vegetation of two cases of endo- 

 carditis following influenza. 



Pathogenesis. The bacillus is pathogenic for very few 

 of the laboratory animals, the guinea-pig being susceptible 

 of fatal infection. The dose required to cause death of a 

 guinea-pig varies considerably. 



Immunity. In the immunization experiments of Deline 

 and Kole t one-twentieth of a twenty-four-hour-old culture 

 was fatal in twenty-four hours. They found that the toxicity 

 of the culture does not depend upon a soluble toxin, but 

 upon an intracellular toxin. The outcome of the researches, 

 which were made most painstakingly, was total failure to 

 produce experimental immunity. 



Fig. 171. Bacillus of influenza; cover-glass preparation of sputum 

 from a case of influenza, showing the bacilli in leukocytes. Highly 

 magnified (Pfeiffer). 



Increasing doses of the cultures, injected into the perito- 

 neal cavity, enabled the animals to resist more than a fatal 

 dose, but never enabled them to maintain vitality when large 

 doses of living cultures were administered. This observation 



* "Path. Soc. of Lond.," "Brit. Med. Jour.," April 22, 1905. 

 f " Zeitschrift fur Hygiene," etc., Bd. xxiv, 1897, Heft 2. 



