Specificity 643 



sato makes a special point of the fact that they never become 

 confluent. The colonies may at times be so small as to 

 require a lens for their detection. 



In bouillon a scant development occurs, small whitish 

 particles appearing upon the surface, subsequently sinking 

 to the bottom and causing a "wooly" deposit there. The 

 bacillus grows more luxuriantly upon culture media contain- 

 ing hemoglobin or blood, and can be transferred from culture 

 to culture many times before losing vitality. 



Vital Resistance. Its resisting powers are very re- 



Fig. 191.- Bacillus of influenza; colonies on blood agar-agar. Low 

 magnifying power (Pfeiffer). 



stricted, as it speedily succumbs to drying, and is certainly 

 killed by an exposure to a temperature of 60 C. for five 

 minutes. It will not grow at any temperature below 28 C. 

 Specificity. From the fact that the bacillus is found 

 chiefly in cases of influenza, that it is present as long as the 

 purulent secretions of the disease last, and then disappears, 

 and that Pfeiffer was able to demonstrate its presence in all 

 cases of uncomplicated influenza, it seems that his conclu- 

 sion that the bacillus is specific is justifiable. It is also 

 found in the secondary morbid processes following influenza, 



