deposit, and there is no reversal of pH in broth. Ten years of observations in all parts of the world have shown (McLeod, Bact. Rev., 7, 1943, 1) that a small percentage of strains does not correspond closely to any of these three types. Variant strains are found most frequently' in regions where the diphtheria is of mild or moderate severity. Aerobic, facultative. Optimum temperature, between 34° and 36° C. Grows well at 37° C. Relationship to other species: A compari- son of cultures has shown Corynebacterium ulcerans Gilbert and Stewart to be identical with C. diphtheriae Lehmann and Neumann (Henriksen and Grelland, Jour. Path, and Bact., 64, 1952, 509). Source: Commonly from membranes in the pharynx, larynx, trachea and nose in hu- man diphtheria; from the seemingly healthy pharynx and nose in carriers; occasionally from the conjunctiva and infected super- ficial wounds. Found occasionally infecting the nasal passages and wounds in horses; also reported from natural diseases in fowl. Habitat: The cause of diphtheria in man. Pathogenic to guinea pigs, kittens and rab- bits. For action on other animals see An- drewes et al. (Diphtheria. London, 1923, 170 ff.). 2. Corynebacterium enzymicum (IVIel- lon, 1917) Eberson, 1918. (An unusual diph- theroid bacillus, Mellon, Med. Record, New York, 81, 1916, 240; Bacillus enzymicus Mel- lon, Jour. Bact., 2, 1917, 297; Eberson, Jour. Inf. Dis., 23, 1918, 29.) en.zy'mi.cum. Gr. noun zynie leaven; M.L. noun enzymum enzyme; M.L. adj. enzymicus relating to enzyme. Rods, beaded and club-shaped, definitely pleomorphic, showing coccoid forms. Non- motile. Gram-positive. Gelatin stab: Slight surface growth. No liquefaction. Glucose agar: Bacillary form shows very small colorless colonies. Coccoid form shows heavy, yellowish white, moist growths. Blood agar: Same as on glucose agar. Loefiier's blood serum: Fine, moist, con- fluent growth. Glucose broth: Bacillary form shows granular sediment. Coccoid form shows diffuse, luxuriant growth. Litmus milk: Acid, coagulated. Potato: No growth. Indole production slight. Acid from glucose, maltose, sucrose, dex- trin and glycerol. Slight production of nitrites from nitrates. Aerobic, facultative. Optimum temperature, 37° C. Pathogenic for rabbits, guinea pigs and mice. Source: Isolated from lungs, blood and joints. Habitat: From human sources so far as known. 3. Corynebacterium hoagii (Morse, 1912) Eberson, 1918. (Bacillus X, Hoag, Boston Med. and Surg. Jour., 167, 1907, 10; Bacillus hoagiiMoTse, Jour. Inf. Dis., 11, 1912, 284; Eberson, Jour. Inf. Dis., 23, 1918, 10.) hoa'gi.i. M.L. gen. noun hoagii of Hoag; named for Dr. Louis Hoag, the bacteriolo- gist who first isolated this species. Rods, 0.8 to 1.0 by 1.0 to 3.0 microns, oc- curring singly. Show polar staining in the shorter forms while the longer forms are barred and slightly club-shaped. Non-mo- tile. Gram-positive. Gelatin colonies: Small, dull, pale pink, entire. Gelatin stab: Slight pink surface growth. No liquefaction. Agar colonies: Small, pale pink, dull, granular, entire. Agar slant: Filiform, dull, pink growth. Broth: Turbid, with slight pink sediment. Litmus milk: Slightly alkaline, with pink sediment. Potato: Dull, filiform streak. Indole not produced. Acid from glucose and sucrose but not maltose. Nitrites not produced from nitrates. Blood serum: Dull, filiform, pink streak. Aerobic. Optimum temperature, 30° C. Source: Isolated from the throat; also from air contamination of cultures. Habitat: Unknown.
