NON-SPORING BACILLI 243 



MINUTE BACILLI. 



Under this heading may be conveniently grouped the 

 bacilli, of influenza, of acute epidemic conjunctivitis, and 

 of whooping-cough. All are Gram-negative. 



Bacillus Influenzae Was first described in 1892 by 

 several observers, and has been called after one of them 

 the Pfeiffer bacillus. It is very small even among micro- 

 organisms, being only from 0-5 to 1-2 micron long by 0-2 to 

 0-4 micron thick. A tubercle bacillus, 3 micra by 0-3 

 micron is thus equal in length to several (3 to 6) influenza 

 bacilli placed end to end. 



It is then a small bacillus, of irregular length, having 

 rounded ends, rarely forming chains, non-motile, non- 

 sporing, Gram-negative, and not growing on gelatin or at 

 room temperatures. It is not easily stained with the usual 

 dyes ; best with 10 per cent aqueous fuchsin, or Loeffler's 

 methylene-blue, 5 minutes of either. The bacilli form 

 irregular clusters ; occasionally polar staining is noticed. 



Cultures. It is not easily cultivated, growing only in 

 the presence of haemoglobin. This is obtained on the 

 ordinary media by smearing them with some blood drawn 

 from the finger, or by mixing melted agar with fresh blood. 

 The blood of the pigeon may be used. The medium is 

 inoculated w r ith the sputum coughed up from the bronchi, 

 avoiding mucus from the mouth. Colonies appear in 18 

 to 24 hours, as minute transparent drops, colourless, and 

 likened to drops of dew. Growth ceases in 2 to 3 days. 

 Frequent subculturing and storage at room temperature 

 are needed to keep the cultures alive. 



It is aerobic, and shows no growth under strict anaero- 

 biosis. It is readily killed at 60 C. ; and by drying, in 

 a few hours. Dies in culture media within a week. Its 

 usual habitat during an epidemic is the nasal passages 

 and bronchial tubes. It is said to remain in these 

 places after recovery from the attack, and to persist for 

 years. The immunity produced by an attack of influenza 

 is very short. A pseudo-bacillus, differing only in its 

 slightly larger size and its growth in threads, and showing 

 involution forms, has been described, but its differentiation 

 is doubtful. 



