CHAPTER XXIII. 



THE INFLUENZA AND PSEUDOINFLUENZA BACILLI THE KOCH- 

 WEEKS BACILLUS. 



The Influenza Bacillus. Influenza as a distinct entity can be 

 traced back to the fifteenth century and probably existed at a much 

 earlier date. 



At times but few endemic cases occur and then a great epidemic 

 spreads over the civilized world. The last great epidemic reached 

 Russia from the East in the fall of 1889 and gradually spread over 

 Europe and to America, reaching the latter country in December of 

 that year. Since then we have had more or less of it, especially during 

 the winter months. 



FIG. 100 



Influenza bacilli. X 1100 diameters. 



The rapidity of the spread of epidemics of influenza suggested that 

 persons were the carriers of the infection, while the location of the 

 disease pointed to the respiratory tract as the location of and to the 

 expectoration as the chief source of infection by the micro-organisms. 



After numerous unsuccessful attempts, during the epidemic of 1889 

 and succeeding vears, to discover the specific cause of influenza, Pfeiffer 

 (1892) succeeded in isolating and growing upon blood agar a bacillus 

 which abounded in the purulent bronchial secretion of patients suffer- 

 ing from epidemic influenza, which he showed was the probable cause 

 of the disease. This bacillus was not found upon normal respiratory 

 mucous membranes. 



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