396 BIOLOGY OF THE LABORATORY MOUSE 



subcutaneous injection. The lesions are similar to those in the spontaneous 

 disease, except that the lungs are seldom infected. Inoculation into a serous 

 cavity results in a rather characteristic granular exudate over the serosal 

 surfaces, which may take the form of tiny, discrete nodules or coalesce to 

 form a membrane. The liver is infrequently affected, but lesions occur in 

 the spleen and kidneys. Perinephric abscesses and pyonephritis may 

 rarely be present. Diaphragm, heart, voluntary muscles, and subcutaneous 

 tissues may all show nodules. It is interesting, in view of the polymorphism 



of this organism and its similarity to 



the streptothrix, that involvement of 



,^ »- , -« f. ^- ^ the joints may occur (216). Infec- 



^ «,, %• "» . , , '• C " „ . tion by mouth produces lesions 



i^J"Z ^ i. '•*.'J •'. :^ .7' ^ chiefly in the mesenteric glands and 



y J. Lin , -sC^-*- occasionally in the abdominal viscera. 



"* '/ *f .'-*"' ,^- * Microscopic examination reveals 



4. ^fV "t" "rf ■ ** ^* that the nodules or "tubercles" are 



4^ , ***-«' *if'^. .. composed of bacteria with varying 



%"* * "*•** '•'•*' ''' - degrees of cellular infiltration. The 



"' ^'' "% f^ '"*>.. ,'^t j*^" picture is not one of cellular prolifera- 



^ Tt **^^J ' *]?' ' tion. The serosal nodules and mem- 



"^ ^^^ branes consist of bacteria and a small 



Fig. 153.— Pseudotuberculosis of mice, number of cells, but no fibrin. In 



Morphology of Corynehacleriitm kutscheri lesions of longer duration, the appear- 



grown on agar. Loeffler's stain. Photo- ^j-,^,^ ^g ^^at of a pyogenic abscess with 



micrograph (X1500). {From Andrcwcs, suppuration and necrosis. Bacteria, 



which are abundant, group them- 

 selves into definite colonies in the tissues and particularly on serous surfaces, 

 appearing as masses of interlacing filaments. Thrombi and organisms 

 are found within blood vessels. 



Occasionally at autopsy the only lesion is a small abscess at the site 

 of inoculation. Bongert (25) postulated the production of a toxin to explain 

 these instances, and demonstrated that filtrates of broth cultures or heat- 

 killed organisms could cause death in 10 to 14 days without obvious lesions. 

 Topley and Wilson (287) have confirmed this finding and consider that the 

 organism produces an exotoxin which is lethal for mice. 



Etiology. — The etiological agent is Corynehacterium kutscheri Bergey (22) 

 {B. pseudotuberculosis murium Kutscher, Corynethrix pseudotuberculosis 

 murium Bongert) (Fig. 153). It is a true diphtheroid, occurring as slender 

 granular rods with some club forms in young cultures, but showing a great 



