Genus II. Actinomyces Harz, 1877. (Harz, in Bollinger, Cent. f. med. Wissensch., 15, 1877, 485; also see Jahresber. d. Munch. Thierarzeneischule fiir 1877-78, 1879, 125; not Actinomyce Meyen, Linnaea, £, 1827, 442; Cohnistreptothrix Pinoy (in part), 1911, see Pinoy, Bull. Inst. Past., 11, 1913, 929.) Ac.ti.no.my'ces. Gr. noun actis, actinis ray; Gr. noun myces fungus; M.L. mas.n. Ac- tinomyces ray-fungus. True mycelium produced. The vegetative mycelium fragments into elements of irregular sizes and may exhibit angular branching. No conidia produced. Not acid-fast. Anaerobic to microaerophilic. Pathogenic for man and other animals. The type species is Actinomyces hovis Harz. Key to the species of genus Actinomyces. I. Colonies soft, smooth, uniform, not adherent to medium. No aerial hyphae. 1. Actinomyces hovis. II. Colonies tough in texture and warted in appearance, adherent to medium. Scant aerial growth of hyphae. A. Hyphae in pus granules stain with acid stains. 2. Actinomyces israelii. B. Hyphae in pus granules stain with basic stains. 3. Actinomyces baudetii. 1. Actinomyces bovis Harz, 1877. (Harz, in Bollinger, Cent. f. med. Wissensch., 15, 1877, 485; also see Jahresber. d. Mlinch. Thierarzeneischule fiir 1877-78, 1879, 781.) bo'vis. L. noun 60s the ox; L. gen. noun bovis of the ox. Description taken from Erikson (Med. Res. Council, London, Spec. Rept. Ser. 240, 1940, 63 pp.). No aerial hyphae. Radiate, sulfur-colored granules occur in the pus found in cases of actinomycosis. Large club-shaped hyphae are seen in morbid tissues. Mycelium under- goes fragmentation very rapidly, extensive branching being rare. Hyphae less than 1 micron in diameter. Non-motile. Not acid- fast. Gram-positive. Colonies: Smoother and softer in con- sistency and more uniform than those of the following species. The colonies are not adherent to the medium, and growth is scantier. Semi-solid media: Excellent growth, especially with paraffin seal. Gelatin: Occasionally scant, flaky growth. No liquefaction. Liquid media: Occasionally turbid with a light, flocculent growth. Acid from glucose, sucrose and maltose. No acid from salicin or mannitol. Pigments: No soluble pigments produced on protein media. No insoluble pigments produced by growth. Egg or serum media: No proteolytic ac- tion. Litmus milk: Becomes acid but usually no coagulation, no peptonization. Some- times no growth. No hemolysis in blood broth or blood agar. Anaerobic to microaerophilic. Bovine strains are more oxygen-tolerant on egg or serum media than strains of human origin belonging to the following species. Optimum temperature, 37° C. Serology: No cross agglutination between five bovine strains and human strains of Actinomyces israelii. No cross reactions with representative aerobic strains. Comments: As pointed out by Lignieres and Spitz (Bull. Soc. cent. M6d. vet., 20, 1902, 487 and 546) and others, distinction should be made between the infections pro- duced by Actinomyces bovis and those pro- duced by the Gram-negative Actinobacillus now known as Actinobacillus lignieresii. These infections frequently occur in mixed form and are also frequently complicated by the presence of pj'ogenic cocci (Magnus- sen, Acta path. Microbiol. Scand., 5, 1928, 170; and others). Relationships to other species: This and the following species are sometimes re-
