INFECTIOUS DISEASES OF MICE 389 



pale and swollen. The disease resembled a chronic intestinal infection in 

 which the etiological agent was unable to penetrate the intestinal mucosa 

 and invade the body tissues. The mortality among infected animals was 

 100 per cent. A motile, gram-negative bacillus isolated at autopsy was 

 identified as Morgan's bacillus. This organism closely resembles those of 

 the Salmonella group in many of its properties, although it is now classified 

 in the proteus group {Proteus morgani) (287, 22). Attempts to feed mice 

 and reproduce the infection experimentally almost completely failed, so 

 that a part, at least, of the etiological factors remains unknown. 



Syverton and Olitsky (265) have carefully studied an unusual epidemic 

 of acute intestinal infection sharply limited to suckling and newly weaned 

 Swiss mice. The clinical signs were those of profuse diarrhea with apparent 

 tenesmus and marked inanition, rapid loss of weight and tone, complete 

 prostration in 24 to 72 hours, and death in about one-half of the affected 

 animals. Obstipation and cessation of suckling sometimes supervened to 

 produce a state of dehydration that was almost uniformly fatal. If recovery 

 occurred, necrosis and sloughing of the perianal tissues frequently followed. 

 In the absence of obstipation, recovery was usually complete. The age 

 incidence was from 7 to 24 days. 



The gross pathological changes varied from slight h5^eremia to necrosis 

 of the lower ileum and colon. The spleen was dark red and contracted; 

 in recovered cases it frequently showed gross cicatrization. Microscopically, 

 characteristic changes were present in the lower ileum and colon. The 

 involvement of the intestines was extensive and consisted chiefly of leuko- 

 cytic and erythrocytic infiltration and generalized ulceration of the mucosa 

 to such an extent that the latter was often found as a slough in the lumen of 

 the bowel. Hypertrophy of Peyer's patches was particularly marked. 

 The spleen was hemorrhagic with varying degrees of necrosis of the pulp 

 cells. DifTuse parenchymatous and fatty degeneration and localized 

 hemorrhages were noted in the liver. Renal congestion, localized hemor- 

 rhages, and degeneration of tubular epithelium were present. In the brain, 

 minute focal hemorrhages were frequently found. 



From the intestine, and less frequently from the heart's blood, liver, and 

 spleen, organisms of the genus Salmonella were cultured. Of 20 strains, 

 13 were serologically identical; the other 7 behaved serologically as a single 

 variant. All were culturally identical. Significant cross-agglutinations 

 were not obtained with antisera against known Salmonella strains. 

 Specific agglutinins for both types were present in the sera of one-third 

 of the recovered mice, but not in those of normal animals. The disease 



