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414 BIOLOGY OF THE LABORATORY MOUSE 



tympanic cavity was tilled with a copious, purulent exudate containing 

 many white blood cells. The pneumonia, which was progressive and finally 

 resulted in death of the animal, was usually lobar in distribution. The 

 involved area was consolidated, contracted, and red, grey, or mottled in 

 color. In advanced cases, all lobes were sometimes involved. Bronchial 

 exudate of polymorphonuclear cells, secondary alveolar extension as indi- 

 cated by leukocytes, erythrocytes, large mononuclear cells, and fluid in the 



alveoli, and hyperplasia of the 

 peribronchial lymphoid tissue were 

 the chief features microscopically. 



In stained films of exudate from 

 the nares, middle ears, and lungs of 

 diseased animals were found small 

 gram-negative cells, termed "cocco- 

 bacilliform bodies" because of their 

 * similarity to those of fowl coryza 

 { (Fig. 160). The organisms were 



generally spherical, but rod-shaped 

 cells and ring forms were seen. 

 -^k rhey occurred singly, in pairs, and 



1 • in loose clumps. Although pre- 

 dominantly extracellular, they were 

 Fig. 160. -Infectious catarrh o! mice; ^j^^ f^^j^^ -^^ polymorphonuclear 

 scattered extracellular coccobacilhform j^^j^^^^^ ^^^ epithelial cells, 

 bodies in nasal exudate. Gram stain. -^ 1 • 1 



(X920.) {From Nelson.) Attempts to cultivate the organism 



on "ordinary nutrient media 

 enriched with blood" were unsuccessful, although growth occurred in tissue 

 culture and in the supernatant fluid of tissue culture media. In several 

 instances, pure cultures of the coccobacilliform bodies were obtained, 

 especially from the middle ear; in others, the organism was found in associa- 

 tion with staphylococci, streptococci, or an unidentified short, non-motile 

 gram-negative bacillus, termed the "X" bacillus. 



The average diameter of the coccobacilliform bodies by direct micro- 

 scopy was between 0.3 and 0.4 ^t. The bodies passed through a collodion 

 membrane with an average pore size of 640 m^t, which indicates an average 

 particle diameter of 480 m^. Such filtration, however, did not separate the 

 organism from the X bacillus. 



The etiological relationship of the coccobacilliform bodies to mouse 

 catarrh seems to be established since the disease was reproduced by pure 



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