INFECTIOUS DISEASES OF MICE 



395 



pleural effusion and a slightly enlarged spleen. Organisms were abundant 

 in the caseous mass in the right lung and in the nodules of the left lung. 



Pulmonary lesions are almost always found in the severe disease, and, 

 in fact, may frequently be the only signs of the disease (287, 25). Involve- 

 ment of the lung varies from pin-head sized lesions to caseation of an entire 

 lobe associated with pleural effusion. Recent mihary lesions have a trans- 

 parent greyish-blue center surrounded by a dark red inflammatory zone 

 which is sharply outlined. Microscopically, the normal pulmonic architec- 



FlG. 



-Pseudotuberculosis of mice. Spontaneous infection. Viscera of mouse 

 {in situ) showing lesions. {From Bongert.) 



ture is not visible in the nodules. At the periphery of the lesions numerous 

 bacilli are seen, both intra- and extracellularly. The liver infrequently 

 contains yellowish-white caseous nodules which are raised when located in 

 the subcapsular region, thus diiTering from the necrotic foci characteristic 

 of Salmonella infection. Glandular enlargement and caseation, either focal 

 or generalized, may be found particularly in the mediastinal, mesenteric, 

 and cervical nodes. Isolated nodules may occur in the spleen and kidneys. 

 Occasionally, only the abdominal viscera are involved (Fig. 152). 



The experimental disease. — Experimentally, the disease is specific for 

 mice, and can be produced by subcutaneous, intraperitoneal, intrathoracic, 

 and oral routes, and by inhalation. Death usually occurs in 3 to 5 days 

 and rarely later than 14 days, even following infection per os. The patho- 

 logical findings vary somewhat with the route of infection. Generalized 

 infection follows parenteral inoculation, a local abscess occurring after 



