infection in swine involving the serous mem- branes of the thoracic and abdominal cav- ity. The relationship of this organism to atrophic rhinitis seems to require further study. 8. Mycoplasma pulmonis (Sabin, 1941) Freundt, 1955. (L3 , Klieneberger and Steab- ben, Jour. Hj^g., 37, 1937, 143; Murimyces -pulmonis Sabin, Bact. Rev., 5, 1941, 57; Freundt, Internat. Bull, of Bact. Nomen. and Taxon., 5, 1955, 73; also see Edward, Internat. Bull, of Bact. Nomen. and Taxon., 5, 1955, 91.) pul.mo'nis. L. noun pulmo the lung; L. gen. noun pulmonis of the lung. Unstable, sparsely branched mj^celioid structure with very short, almost bacillary filaments which usually measure 2 to 5 mi- crons in length (0rskov, Acta Path, et Mi- crobiol. Scand., 19, 1942, 575; Freundt, un- published observation). Elementary bodies and short rods have been demonstrated in electron micrographs by Klieneberger- Nobel and Cuckow (Jour. Gen. Microbiol., 12, 1955, 95). Gram-negative. Horse-serum agar: A film and spots are produced. Central spot of the colonies is less marked than those of most of the other species in this genus; rough surface. Horse-blood agar: Alpha hemolysis. Rabbit-serum agar: Poor growth. Semi-solid media: Granular growth, pref- erably near the surface. Broth: Granular growth. Acid from glucose, mannose, maltose, glycogen, dextrin and starch. No acid from fructose, galactose, sucrose, lactose, salicin, mannitol or dulcitol. Methylene blue is slowly reduced. Aerobic; very poor growth under an- aerobic conditions. Serologically different from Mycoplasma arthritidis Freundt. Pathogenicitj-: Produces suppuration in mice when injected along with agar. Not pathogenic for rats in artificial infection. Sometimes found in young rats without definite lung lesions, while in older rats a close connection has been demonstrated between the presence of this organism and bronchiectatic pulmonary disease; however, the etiological significance of this organism to this condition seems obscure. Experi- ments reported by Klieneberger-Nobel and Cheng (Jour. Path, and Bact., 70, 1955, 245) suggest that the role of this organism may be that of a secondary invader. Comment : The isolation of closelj^ related organisms from mice with infectious catarrh has been reported by Edward (Jour. Gen. Microbiol., 10, 1954, 27). Source: Isolated from the lungs of labora- tory rats, most of which had bronchiectasis although some were without lesions; also isolated from a wild rat. Habitat: From the normal and diseased lungs of rats so far as definitely known. 9. Mycoplasma arthritidis (Sabin, 1941) Freundt, 1955. (L4 , Klieneberger, Jour. Hyg., 38, 1938, 458; Murimyces arthri- tidis Sabin, Bact. Rev., 5, 1941, 57; Pleuro- pneumonia arthritidis muris Tulasne and Brisou, Ann. Inst. Past., 88, 1955, 238; Freundt, Internat. Bull, of Bact. Nomen. and Taxon., 5, 1955, 73; also see Edward, Internat. Bull, of Bact. Nomen. and Taxon., 5, 1955, 91.) ar.thri'ti.dis. Gr. noun arthritis gout, arthritis; M.L. gen. noun arthritidis of ar- thritis. Unstable to relatively stable mycelioid structure; filaments vary from short, almost bacillary forms (usually 2 to 5 microns in length) to moderately long structures (10 to 30 microns) (Preston, Jour. Inf. Dis., 70, 1942, 180; Freundt, unpublished obser- vation). Gram-negative. Horse-serum agar: Neither film nor spots are produced. Horse-blood agar: Alpha hemolysis. Rabbit-serum agar: Good growth. Semi-solid media: Fluffy growth through- out. Broth: Slight, uniform opalescence. Carbohj'drates not attacked. Methylene blue is slowly reduced. Aerobic, facultatively anaerobic. Serologically distinct from Mycoplasma pulmonis Freundt. Pathogenicity: When injected together with agar intravenously or into the pads of rats and mice, the organism appears to have
