INFLUENZA 177 



Staining Reactions. The bacillus stains with difficulty. Loffler's 

 methylene blue is a good stain, but a pale red solution of carbol fuchsin 

 in water is better. The preparation must be stained five to ten minutes ; 

 if stained for a shorter time or with other stains the middle portion of 

 the rod is often lighter coloured than the end portions. The results 

 with the Gram method are negative. 



Biological Characters. The influenza bacillus is strongly aerobic, 

 and grows only in the presence of haemoglobin or leucocytes. These 

 latter conditions explain why the cultivation of the influenza bacillus was 

 so long a failure. 



Pfeiffer was able sometimes to obtain cultures from lung pus direct 

 on agar, but at other times it was impossible. The cause of the irregu- 

 larity was that the rods in the first cultures developed when a trace of 

 blood was inoculated with the material, the growth being negative 

 when no blood was present, the same peculiarity applying to all the 

 daughter cultivations. The influenza bacillus can be cultivated regularly 

 and transferred through several generations in nutrient media containing 

 blood. Blood agar is the best medium. To obtain pure cultures 

 Pfeiffer employs the following method : 



The bronchial sputum or exudate from the broncho-pneumonic 

 infiltrated portion of the lung in influenza-pneumonia is thoroughly 

 emulsified with 1 to 2 c.c. of bouillon. Several platinum loops of the 

 bouillon are inoculated, and thoroughly spread over the whole surface of 

 blood agar media, and at the same time control cultures are instituted on 

 ordinary glycerine agar medium. 



The dilution of the bouillon has the effect of segregating influenza 

 bacilli, so that they grow in separate colonies on the blood agar medium, 

 while any haemoglobin present in the original material is so thoroughly 

 diluted, that the influenza bacillus cannot develop on the control agar 

 tubes containing no blood. 



The inoculated tubes are placed in the incubator, and in twenty-four 

 hours the influenza colonies appear on the surface of the blood agar 

 medium as closely compressed transparent drops. The control tubes 

 are either sterile or contain colonies of streptococci, diplococci, or other 

 bacteria associated with the influenza bacillus in the original material. 



The transparent drops of the influenza colonies are mostly so small 

 that they can only be distinctly seen with a hand lens. They possess a 

 slight tendency to become confluent, and when closely arranged they 

 coalesce into large curved limited drops, the individual arrangement of 

 the colonies being still apparent. When the colonies are widely separ- 

 ated from each other, they sometimes develop as large as a pin-head, 

 and still retain their glassy transparent appearance. The condensation 

 water in the tubes remains usually clear, except when it is mixed with 

 blood that has fallen down the oblique surface of the medium, then 

 delicate white flakes develop in it. 



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