K. F. MEYER 633 



Okamoto/ and others). In fact, Zwick^ found 28 fecal carriers among 177 mice, and 

 Heuser-' claims that 10 per cent of the common laboratory mice may be infected. In 

 this connection it was noted that a severe case of enteritis could be incited in the 

 carrier animals provided certain environmental factors were changed or the animals 

 fed on a protein-high diet."* 



Spontaneous epidemics of mouse typhoid with mortalities from 34 to 95 per cent 

 (Pritchett, Savage and Read,^ the writer) although very common have rarely been 

 investigated and the first published account was given by Lynch^ in 1922. On the 

 other hand, Danysz,^ who endeavored to exterminate rodents on a large scale through 

 employment of living cultures of an organism isolated by him from an epidemic among 

 field mice (B. enter itid is), noted that the infective power by ingestion would not 

 extend beyond a very few passages. He therefore conducted a number of experiments 

 which foreshadowed the extensive experimental investigations conducted by Topley, 

 Webster, and others. These fundamental studies are so recent that a detailed ac- 

 count appears unnecessary, although the essential facts may be mentioned. As a 

 rule the anatomical lesions of the infected mice consist of an engorged spleen with or 

 without definite necroses, foci in the liver, enlarged mesenteric lymph nodes with 

 petechiae, and a gastro-enteritis of varying intensity. The causative organism is al- 

 ways a representative of the paratyphoid-enteritidis group. B. aertrycke is probably 

 the most common infecting agent (in the experience of the writer) but B. enteritidis 

 has also been isolated (Wherry and Butterfield,^ Ten Broeck,' Amoss and Hasel- 

 bauer,'") and "suipester variants," both enteritidis and "animal paratyphoids," were 

 encountered by Topley, Weir, and Wilson" in mouse epidemics. The majority of 

 epidemic strains are virulent for mice per os in relatively small doses. The bacteria 

 multiply in the intestinal tube (lower end of the ileum), penetrate the mucosa, invade 

 the bloodstream and the various tissues, or they localize in the spleen (Smith and 

 Tibbets).'^ The bacilli are discharged from the intestines during the acute disease 

 and from the carriers for some weeks. Contact infections occur among normal mice 

 kept in the same cages and provided a certain degree of uncleanliness is maintained 

 even in the adjacent cages. In this manner interesting epidemics with strikingly 

 constant characteristics may be produced and maintained for an indefinite period 

 of time on the sole condition that susceptible mice are added from time to 

 time to the stock animals. The introduction of fresh individuals from the same or 



' Okamoto, T.: loc. cil. 



^ Zwick, X.: Arb. a. d. kaiserl. Gesimdheitsamle, 133, 250. 1909-10. 



3 See Uhlenhuth, P., and Hiibener, E.: loc. cil. 



■•See also Webster, L. T.: op. cit., 37, 21. 1923. 



s Savage, W. G., and Read, W. J.: /. Hyg., 13, 343. 1913. 



^ Lynch, C. J.: /. Exper. Med., 36, 15. 1922. 



'Danysz, J.: Afin. de VInst. Pasteur, 14, 193. 1900. 



« Wherry, W. B., and Butterfield, C. T.: /. Inject. Dis., 27, 315. 1920. 



'Ten Broeck, C: /. Exper. Med., 32, 19. 1920. 



'"Amoss, H. L., and Haselbauer, P. P.: ibid., 36, 107. 1922. 



" Topley, W. W. C, Weir, H. B., and Wilson. G. S.: /. Hyg., 20, 227. 1921. 



" Smith, T., and Tibbets, H. A. M.: /. Exper. Med., 45, 337. 1927. 



