Tim BACILLUS OF IXFLUENZA. 373 



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 -w-ith 

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



It develops only at temperatures ranging from 26° 

 to 43° C. Its optimum temperature for growtli 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 

 in sterile bouillon or water and rubbed over the sur- 

 face of the prepared agar-agar. The plate or tube is 

 then placed in the incubator at 37° to 38° C. If in- 

 fluenza bacilli be present, they will develop as minute, 

 transparent, watery colonies that are without structure, 

 and which resemble somewhat minute drops of dew. 

 They are discrete and show little or no tendency to 

 coalesce. 



If a small bit of mucus be rubbed over the surface 

 of ordinary nutrient agar-agar, no such colonies de- 

 velop. In making the diagnosis by this method cult- 

 ures on both agar-agar containing blood (not blood- 

 serum) and agar-agar containing no blood should always 

 be made, for the reason that growth of these peculiar 



