57 

 BACILLUS PSEUDO-TUBERCULOSIS RODENTIUM (PFEIFFER). 



This organism that infects rats is of interest from its close resem- 

 blance to the plague bacillus. It is difficult to distinguish the two 

 organisms by ordinary cultural or animal tests. The earlier writers 

 claimed that B. pseudo-tuherculosis rodentium could be differentiated 

 by its power of coagulating milk, but more recently this difference 

 has been found to be an inconstant one. 



TOYAMA'S BACILLUS. 



Toyama has described an organism which he states is pathogenic 

 for Mus rattus, field and house mice {Mus musculus), but not patho- 

 genic for Mus norvegicus. 



It causes congestion of lungs, enlargement of lymph nodes, espe- 

 cially in the neck, and enlargement of the spleen. It was isolated 

 from a natural epizootic among Mus rattus. It is a nonspore-bearing 

 bacillus, without capsule, stains without showing bipolarity, and grows 

 upon ordinary media. 



Among other bacteria that have been described as causing diseases 

 in rats may be mentioned : 



Von Schilling's iaciUus, allied to Danysz's organism. 



Bacillus " Eris," a member of the colon group. 



Bacillus muris, a member of the B. diphtheria group. 



Of the bacteria that show virulence for rats under laboratory con- 

 ditions, but, so far as is known, cause no spontaneous outbreaks, the 

 following are the best-known examples : 



Bacillus hovisepticus produces a fatal disease bacillus of swine 

 erysipelas (especially for albino rats), and the bacillus of tetanus. 



Of the higher fungi (not strictly bacterial) we have: 



Streptothrix madurse, produces local swellings when inoculated 

 artificially. 



It has been stated that rats occasionally suffer from a disease 

 similar or identical to the affection in man known as favus {Ach(yrion 

 Schonleinii). 



INFECTIONS OF MICE (MUS MUSCULUS). 



This specie of Mus is very susceptible to a large number of bac- 

 terial diseases when inoculated under laboratory conditions. The 

 f oUowiug are some of the best-known examples : 



B. murisepticus, Staphlococcus pyogenes, Streptococci, Diplococcus 

 pneumoniae, B. pneumonix (Friedlander), Diplococcus of pleuro-pneu- 

 monia of horses, B. Typhi murium, B. anthracis, B. of mahgnant 

 edema, B. tetani, B. mallei, B. diphtheria vitulorum, B. hovisepticus, 

 B. suisepticus, the bacillus of Mereshkowsky, and many others. 

 The last-named organism has been utilized to a limited extent for the 

 destruction of mice about dwellings. 



