INFECTIOUS DISEASES OF MICE 399 



.stij)atcd. Ivcspiralion decreases in rate, and deatli occurs almost im- 

 l)erceptibly. The pathological lindings are essentially those described 

 above. Mice and rats are susceptible to infection, guinea pigs and rabbits 

 resistant . 



Erysipclolhrix muriscptica {B. murisepticus) is one of three organisms 

 {E. rliusiopat/iiae, E. erysi peloides) which are indistinguishable morphologi- 

 cally, culturally, and serologically. Occasional differences in pathogenicity 

 occur — the murine organism, for example, usually does not infect hogs as 

 does the swine erysipelas strain {E. rhusiopatJiiae) — but are not constant 

 enough to permit classification on that basis. The organisms appear as 

 slender, gram-positive, non-motile rods and as long filaments of threads 

 with irregular thickenings and branching. They are facultative aerobes 

 and grow readily in dew-drop colonies on ordinary agar. In gelatin stab 

 cultures a characteristic "test tube brush" appearance is seen after 3 to 

 5 days at room temperature- fine threads radiate horizontally into the 

 medium from a central mass of growth along the needle track. No liquefac- 

 tion is produced. In broth, a slimy viscous growth occurs which settles to 

 the bottom of the tube. The fermentative reactions vary widely, but in 

 general acid is produced in dextrose, lactose, sucrose, maltose, galactose, 

 and rafiinose after 48 hours' incubation. Hydrogen sulphide is formed; 

 nitrate reduction is variable. Indol is not produced. Serologically, the 

 organism agglutinates with commercial swine erysipelas serum or antiserum 

 produced with any strain of the group. 



The infrequent occurrence of the disease in mice renders its control of 

 little practical importance, but active and passive immunization should be 

 feasible. 



Diseases Due to Infection with the Streptobacillus and Pleuro- 



PNEUMONIA-LIKE ORGANISMS ArTHRITIS OF MiCE 



In 1929 Levaditi and Selbie (151) isolated a strain of Streptobacillus 

 moniliformis from two mice which had been injected with an emulsion of 

 the brain and spinal cord from an apparently normal mouse. Similar 

 organisms had been isolated previously from human patients in France 

 (148) and in America {Haverhillia multiformis) (198). Subsequent work 

 has shown that these organisms are identical with the older Streptothrix 

 muris ratti, and the name of Actinomyces muris has been proposed by Topley 

 and Wilson (287). In view of common usage, however, the name of 

 Streptobacillus moniliformis will be retained here. The organism has been 

 found not only as an inhabitant of the nasopharynx and tissues of apparently 



