CHAPTER XXI. 
HEMOGLOBIXOPHILIC BACILLI: KOCH-WEEKS, 
MORAX-AXENFELD AND DUCREY BACILLI. 
BACILLUS INFLUENZA. 
Bacillus influenzae was isolated in pure culture and described bv 
Pfeifter.i 
Morphology.— It is an extremely small bacillus, one of the smallest 
known, measuring from 0.2 to 0.3 micron in diameter and from 0.5 
to 1 micron in length. The ends are rounded and it occurs singly or 
in pairs, rarely in short chains. The organism is non-motile, and no 
flagella have been demonstrated. Spores and capsules are not pro- 
duced. Ordinary anilin dyes do not color the organism readily, 
but Pfeiffer- has shown that dilute carbol-fuchsiu'^ stains it readily. 
Stained with methylene blue or dilute carbol-fuchsin, the ends of the 
bacilli are colored somewhat more deeply than the center, suggesting 
a bipolar distribution of the cytoplasm similar to that exhibited by 
the bacteria of the hemorrhagic septicemia group. The organism is 
Gram-negative. 
Isolation and Culture.— B. influenzae is an obligately hemoglobin- 
ophilic organism; it does not grow outside the body in the absence 
of hemoglobin, although the amount of this substance required to 
encourage development may be so small in amount that it is invisible 
to the eye.'* Davis'^ has found that 1 part of hemoglobin in 180,000 
is sufficient for many strains. Jacoby and P>ankenthal'' claim that 
histidine, an important constituent of hemoglobin, may replace the 
latter in cultural media. The organism may be isolated from bronchial 
mucus by Pfeiflfer's method. The mucus is washed several times with 
sterile water to remove extraneous bacteria, then spread upon blood- 
agar plates. Human, pigeon or rabbit blood added to neutral plain 
agar creates a favorable medium for the bacillus. Avery's oleate 
agar'' gives excellent growths of the influenza bacillus. The colonies 
which appear after twenty-four to forty-eight hours' incubation at 
37° C. are very minute, clear and colorless. They may require a 
lens for their recognition. The hemoglobin is not visibly changed in 
appearance and no hemolysis occurs. Massive cultures of influenza 
bacilli may be obtained in blood bouillon. One cubic centimeter of 
1 Deutsch. med. Wchnschr., 1892, 18, 28. 
2 Ztschr. f. Hyg., 1893, 13, 357. ' 1 part carbol-fuchsin, 9 parts water. 
* Ghon and Preyss: Centralbl. f. BaktcrioL, orig., 1902, 32, 90; 1904, 35, 531. 
•'■ Jour. Infec. Dis., 1907, 4, 73. ^ Biochem. Zeitschr., 1921, 122, 100. 
' Jpqr. Am- Med. Assn., 1918, 71, 2050; see page 233 for preparation, 
