CHAPTEE XX. 



INFLUENZA BACILLUS. 



AFTER numerous unsuccessful attempts during the 

 epidemic of 1889 and succeeding years to discover the 

 specific cause of influenza, Pfeiffer succeeded in isolating 

 a bacillus (1892) from the purulent bronchial secretion 

 of patients suffering from epidemic influenza which he 



FIG. 40. 



Influenza bacilli. X 1100 diameters. 



showed was the probable cause of the disease. This 

 discovery has since been confirmed by many observers, 

 the results of whose researches give us reason to believe 

 that this bacillus is the chief etiological factor in the 

 production of influenza. 



