a predilection for the joints. Subcutaneous injection produces diffuse abscesses. Intra- cerebral inoculation causes encephalitis in mice but usually no cerebral symptoms in rats. Intranasal instillation causes pneu- monia in mice. Non-pathogenic for mon- keys, rabbits or guinea pigs. Comments : The description of this species is based on a strain isolated by Preston (Jour. Inf. Dis., 70, 1942, 180) from infected joints of rats. Preston's organism is gener- ally believed to be identical with Kliene- berger's L4 , although it was not typed sero- logically. Moreover, L4 is identical with the pyogenic virus of Woglom and Warren (Jour. Exp. Med., 68, 1938, 513), with L7 of Findlay, MacKenzie, MacCallum and Klieneberger (Lancet, 237, 1939, 7) and probably also with the organisms isolated by Beeuwkes and Collier (Jour. Inf. Dis., 70, 1942, 1). Source: Isolated from the submaxillary gland of a laboratory rat with eye, ear and lung infections (Klieneberger, op. cit., 1938, 458) ; also isolated from a contaminated transmissible sarcoma (Klieneberger, Jour. Hyg., 39, 1939, 260) and from outbreaks of spontaneous polyarthritis in laboratory rats (Findlay et al., op. cit., 1939, 7; Preston, op. cit., 1942, 180). Habitat : From various infected lesions of rats so far as known. 10. Mycoplasma neurolyticum (Sabin, 1941) Freundt, 1955. (A filterable, transmis- sible agent with "neurolytic" properties, Sabin, Science, 88, 1938, 189; also see ibid., 575; L5 , Findlay, MacKenzie, MacCallum and Klieneberger, Lancet, 235, 1938, 1511; Musculomyces neurolyticus, type A, Sabin, Bact. Rev., 5, 1941, 24 and 57; Pleuropneu- monia cerehri-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.) neu.ro.ly'ti.cum. Or. noun neuron nerve; Gr. adj. lyticus able to loose; M.L. adj. neurolyticus nerve-destroying. Unstable to relatively stable mycelioid structure, the filaments varying from short, almost bacillary forms (usually 2 to 5 mi- crons in length) to moderately long sturc- tures (10 to 30 microns) (Freundt, unpub- lished observation). Gram -negative. Horse-serum agar: Neither film nor spots are produced. Horse-blood agar: Alpha hemolysis. Rabbit-serum agar: Poor growth. Semi -solid media: Smooth or granular growth, preferably near the surface. Broth: Generalized opalescence. Acid from glucose, mannose, maltose, dextrin, glycogen and starch. No acid from fructose, galactose, sucrose, lactose, salicin, mannitol or dulcitol. Methylene blue is slowly reduced. Aerobic; poor growth under anaerobic conditions. A thermolabile exotoxin, which causes acute necrosis of the posterior pole of the cerebellum in mice, is produced in vivo and in vitro by the American strains. Serologically distinct from the other mem- bers of this genus. The American and Eng- lish strains of this species appear to be sero- logically and immunologically identical. Pathogenicity: American strains of this organism produce "rolling disease" and other nervous symptoms in young mice after intracerebral, intraabdominal or intrathora- cal injection; older mice sometimes develop a transient, non-destructive polyarthritis after intravenous injection. The English strains are less virulent, and "rolling dis- ease" develops only if the organisms are injected together with agar or a neurotropic virus. Other animals, with the exception of the field-vole, are not susceptible. Source: Isolated from the brain of mice that had developed "rolling disease" dur- ing the course of intracerebral passage of various agents: Toxoplasma (Sabin, op. cit., 1938, 189 and 575), lymphocytic choriomen- ingitis and probably also yellow fever virus (Findlay et al., op. cit., 1938, 1511). Later isolated on a few occasions from the brain of normal mice and almost regularly from the conjunctiva and nasal mucosa of car- riers, and from pneumonic foci of mouse lungs after nasal instillation of various ma- terials (Sabin, Science, 90, 1939, 18; also see op. cit., 1941, 24; Sabin and Johnson, Proc. Soc. Exp. Biol, and Med., U, 1940, 569, and Sullivan and Dienes, ibid., 41, 1939, 620).
