Minute, rod-shaped cells which are sometimes thread-forming and pleomorphic. Non- motile. Gram-negative. Strict parasites, growing only in the presence of certain growth accessor}^ substances. May or may not be pathogenic. Found in various lesions and secre- tions, as well as in normal respiratory tracts, of vertebrates. The type species is Haemophilus influenzae (Lehmann and Neumann) Winslow et al. Key to the species of genus Haemophilus. I. Affect warm-blooded animals. A. Affect the respiratory tract or the conjunctiva. 1. Dependence on V (phosphopyridine nucleotide) and X (hemin) determined. a. Require both V and X for growth. 1. Haemophilus influenzae. 2. Haemophilus aegyptius. 3. Haemophilus suis. 4. Haemophilus haemolyticus. 5. Haemophilus gallinarum. aa. Require either V or X for growth, but not both. b. Require V but not X for growth. 6. Haemophilus parainfluenzae. 7. Haemophilus parahaemolyticus . bb. Require X but not V for growth. 8. Haemophilus aphrophilus. 9. Haemophilus influenzae -murium. 10. Haemophilus ovis. 2. Exact dependence on V and X undetermined. 11. Haemophilus putoriorum. B. Affect the genital region. 1. Require X but not V for growth. 12. Haemophilus ducreyi. 13. Haemophilus haemoglobinophilus. 2. Exact dependence on V and X unknown. 14. Haemophilus citreus. II. Affects cold-blooded animals. Requires diphosphothiamine but not V or X for growth. 15. Haemophilus piscium. 1. Haemophilus influenzae (Lehmann encapsulated. Frequently show a marked and Neumann, 1896) Winslow et al., 1917. tendency to bipolar staining. Non-motile. (Infiuenzabacillus, Pfeiffer, Deutsche med. Gram-negative. Wochnschr., 18, 1892, 28; also see Ztschr. Requires both the factors V and X for f. Hyg., 13, 1893, 357; Bacterium influenzae growth in all media. Lehmann and Neumann, Bakt. Diag., 1 Gelatin colonies: No growth. Aufl., 2, 1896, 187; Winslow, Broadhurst, Gelatin stab: No growth. Buchanan, Krumwiede, Rogers and Smith, ^j^^^ ^^^^ colonies: Small, circular, Jour. Bact., 2, 1917, 561.) in.flu.en'zae. Italian noun influenza influenza; M.L. gen. noun influenzae of influenza. transparent, homogeneous, entire. Satel- litism with Micrococcus. V and X transparent agar colonies: 1 to Common name: The Pfeiffer Bacillus. ^ mm in diameter, bluish sheen or iridescent Very small rods, 0.2 to 0.3 by 0.5 to 2.0 i" transmitted light, microns, occurring singly and in pairs, Blood agar slant: Thin, filiform, trans- occasionally in short chains and at times in parent growth, the form of long threads. Some strains are Chocolate agar slant: Luxuriant growth.
