INFECTIOUS DISEASES OF MICE 



441 



slight meningitis. The significant findings are enlarged spleen, a pale or 

 nutmeg liver, serous pleuritis and peritonitis, lungs which may appear 

 normal or contain small areas of consolidation, and occasionally pale and 

 slightly swollen kidneys. Microscopically, there is generalized proliferation 

 of the reticulo-endothelial cells, interstitial and perivascular round cell 

 infiltration, and interstitial bronchopneumonia. Rarely is there necrosis of 

 i:)arenchymal cells. Blood counts in mice injected intravenously may show 



Fig. 170. — Lymphocylic choriomeningitis. Marked meningitis at the base of 

 the brain of a mouse inoculated intracerebrally with the virus. Eosin and methylene 

 blue. (X130.) {From Traub.) 



a leukocytosis up to 55,000 per c. mm. with a relative and absolute lympho- 

 cytosis and monocytosis. 



Cultures of various tissues from infected animals reveal no bacteria of 

 possible etiological significance, and the disease may be reproduced by the 

 inoculation of filtrates of tissue emulsions after passage through Berkefeld 

 or Chamberland candles. Guinea pigs are particularly suitable for inocula- 

 tion since they are highly susceptible, do not themselves carry the virus, and 

 react with a characteristic clinico-pathological picture due to a slowly 

 progressing pneumonia (292). Intracerebral, subcutaneous, and intranasal 

 routes of inoculation may be employed. 



Properties of the virus. — As already pointed out, the virus of lympho- 

 cytic choriomeningitis is mesodermatropic in nature and is widely distrib- 



