CHAPTER XIII. 

 INFLUENZA. 



BACILLUS INFLUENZA (R. 



General Characteristics. A minute, non-motile, non-flagellated, 

 non-sporogenous, non-liquefying, non-chromogenic, aerobic, pathogenic 

 bacillus, staining by the ordinary methods, but not by Gram's method, 

 and susceptible of artificial cultivation, chiefly through the addition 

 of hemoglobin to the culture media. 



Fig. 169. Bacillus of influenza (Muir and Ritchie). 



Notwithstanding the number of examinations conducted 

 to determine the cause of influenza, it was not until 1892, 

 after the great epidemic of influenza, that Pfeiffer* found, 

 in the blood and purulent bronchial discharges, a bacillus 

 that conformed, in large part, to the requirements of 

 specificity. 



Morphology. The bacilli (Fig. 169) are very small, 

 having about the same diameter as the bacillus of mouse- 



*" Deutsche med. Wochenschrift," 1892, 2; "Zeitschrift fur Hy- 

 giene," 13. 



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