THE BACILLUS OF INFLUENZA. 311 



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. 63.) It is decolorized by the method of Gram. 



Fig. 63. 



BacUlus of influenza in sputum. 



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-matter has been added. Its cultivation 

 is best conducted and its development most satisfac- 

 torily observed by the following procedure : over the 

 surface of a slanted agar tube or over agar-agar solid- 

 ified in a Petri dish smear a small quantity of sterile 

 blood (not blood-serum). A bit of the mucus from the 

 sputum of the influenza patient is then taken up with 

 sterilized forceps or on a sterilized wire loop, rinsed 

 off in sterile bouillon or water and rubbed over the 



