342 



BACTERIOLOGY. 



organism in the secretions of the nose, mouth, and 

 throat of apparently healthy persons. 



This organism, bacillus influenzce, as it is called, was 

 discovered, isolated, cultivated, and described by R. 

 Pfeiffer. 



It is a very small, slender, non-spore-forming, non- 



FIG. 64. 



Bacterium influenza in sputum. 



motile, aerobic bacillus, occurring singly and in pairs, 

 joined end to end. It stains with watery solutions of 

 the ordinary basic aniline dyes ; somewhat better with 

 alkaline methylene-blue, but best when treated for five 

 minutes with a dilution of Ziehl's carbol-fuchsiu in 

 water (the color of the solution should be pale red). 

 (Fig. 64.) It is decolorized by the method of Gram. 



It develops only at temperatures ranging from 26 

 to 43 C. Its optimum temperature for growth is 

 37 C. It possesses the peculiarity of developing upon 

 only those artificial culture-media to which blood or 



