426 APPLICATION OF METHODS OF BACTERIOLOGY 



there can be no doubt that singly or together they are 

 responsible for most of the clinical symptoms and patho- 

 logical changes by which influenza is characterized. 



Bacterium influenzae is a very small, slender, non-spore- 

 forming, non-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 



FIG. 76 



Bacterium influenzae in sputum. 



alkaline methylene-blue, but best when treated for five 

 minutes with a dilution of Ziehl's carbol-fuchsin in water 

 (the color of the solution should be pale red). (Fig. 76.) 

 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 blood-coloring- 



