are frequently short, rarely exceeding 20 microns in length. Gram-positive. Best growth is obtained in an atmosphere of low oxygen tension. Gelatin: No liquefaction. Agar colonies: Dull, whitish granules adhering slightly to the medium. Liquid media: A sediment of white gran- ules is produced. LoefBer's blood serum: In 4 to 5 days the surface is covered with white granules which are the size of a pin head. Serum media: No proteolytic action. Brain extract favors growth in some media. Indole production slight. Acid from glucose, sucrose and starch. Anaerobic to microaerophilic. Optimum temperature, 37° C. Pathogenic when inoculated into dogs, rabbits and guinea pigs where it forms sub- cutaneous abscesses. Distinctive characters: For some j^ears this organism was regarded as identical with Actinomyces israelii. However, recent work by Brion et al. (loc. cit.), Brion (op. cit., 91, 1942, 157), Prevot et al. {op. cit., 81, 1951, 85) and Guyard (Thesis, Fac. de Med. et de Pharm. de Lyon, No. 34, Annee Scolaire 1951-1952) has shown that these two or- ganisms can be differentiated as follows: A. israelii is pathogenic for man and cattle, and the club-shaped bodies at the ends of the hyphae in the pus granules stain with acid stains while those found in A. baudetii absorb basic stains. Source: Isolated from various types of lesions in cats and dogs. Habitat: Cause of actinomycosis in cats and dogs. FAMILY III. STREPTOMYCETACEAE WAKSMAN AND HENRICI, 1943.* (Jour. Bact., 46, 1943, 339.) Strep.to.my.ce.ta'ce.ae. M.L. mas.n. Streptomyces type genus of the family; -aceae ending to denote a family; M.L. fem.pl.n. Streptmnycetaceae the Streptomyces family. Vegetative mycelium does not fragment into bacillarj^ or coccoid forms. Conidia borne on sporophores. Primarilj^ soil forms, sometimes thermophilic in rotting manure. A few species are parasitic. Key to the genera of family Streptomycetaceae. I. Conidia produced in aerial hyphae in chains. Genus I. Streptomyces, p. 744. II. Conidia produced terminally and singly on short conidiophores. A. No growth between 50° and 65°C. Genus II. Micromonospora, p. 822. B. Growth occurs between 50° and 65°C. Genus III. Thermoactinomyces, p. 824. Genus I. Streptomyces Waksman and Henrici, 1943. (Streptothrix Cohn, Beitr. zur Biol, der Pflanzen, I, Heft 3, 1875, 186; not Streptothrix Corda, Prachtflora Europaescher Schimmelbildung, 1839; Waksman and Henrici, Jour. Bact., 46, 1943, 339.) Strep. to. my 'ces. Gr. adj. streptus pliant, bent; Gr. noun myces fungus; M.L. mas.n. Streptomyces pliant fungus. Grow in the form of a much-branched mycelium with a typical aerial mycelium. Conidio-
- Completely revised by Prof. S. A. Waksman, Rutgers University, New Brunswick, New
Jersey, March, 1953.
