GROUP OF SPORE-BEARING ANAEROBES 351 



conditions when in mixed cultures with aerobes. The spores resist 

 desiccation indefinitely. They are also much more than usually 

 resistant to the action of disinfectants. Likewise, resistance to 

 heat is so marked that Theobald Smith found in one case that ex- 

 posure to live steam for seventy minutes failed to destroy the or- 

 ganism, although usually a shorter period suffices. 



. 



Fig. 146. Bacillus tetani, colonies Fig. 147 . Bacillus tetani y deep 



in dextrose gelatin (Frankel and stab culture in dextrose gelatin 



Pfeiffer). (Frankel and Pfeiffer). 



Acids are produced from carbohydrates, and a small amount 

 of gas from dextrose. Enzymes which liquefy gelatin and blood- 

 serum have been demonstrated. 



Pathogenesis. Experimental Evidence. Injection of pure cul- 

 tures of B. tetani into experimental animals causes the develop- 

 ment of a typical tetanus. The white mouse is among the most 

 susceptible of animals to inoculation. Infection of this animal 

 is within one to three days followed by tetanic convulsions and 

 death. Birds are not ordinarily susceptible to infection. The 



