ON EPIDEMICS AMONGST MICE. 299 



After this all the large mice were taken out of the cage, and 

 each isolated in a glass. The large case was emptied, cleaned, 

 and disinfected with a solution of corrosive sublimate of the 

 strength of one per cent. The young mice were then replaced. 



Oct. 27th. Four large isolated mice died (13 — 16). Three 

 small ones died in the cage (17 — 19). 



Oct. 31st. An isolated mouse died (20). 



Nov. 1st. A small one died in the cage (21). 



Nov. 2nd. A large isolated mouse died (22). 



Nov. 7th. Another of the same died (23). With the death of 

 this mouse the epidemic came to an end. In the course of four 

 weeks thirty-one mice had died out of forty-five in the cage, the 

 mortality thus amounting to 69 per cent. The first eight mice 

 were not examined, but all the others were. All those examined 

 had died of the same disease, and no doubt this was the case with 

 the first eight. The epidemic must be regarded as uncommonly 

 fatal. It is highly probable that all the mice would have died 

 if the epidemic had not been arrested by strict isolation and 

 disinfection. 



Nearly all the mice found dead in the large cage had been 

 more or less eaten. The brain was generally gnawed away, and 

 in several cases the bodies were half-devoured. This fact, taken 

 in connection with the observations on the first epidemic, which 

 was caused by the bacilli of " mouse-septicaemia," leads to the 

 suspicion that the infection is caused and multiplied by receiving 

 the cause of the disease per os. Further investigations confirmed 

 this suspicion. 



The appearances, on dissection, were on the whole very 

 similar, but varied considerably in individual cases. On opening 

 the abdominal cavity, a splenetic tumour was almost always 

 observed. The spleen was large, brownish red, and generally 

 solid. The liver was usually parenchymatously turbid. It generally 

 displayed a very large amount of fatty matter, and sometimes also 

 showed small yellow specks. Sometimes the liver was very full 

 of blood, and sometimes dry and shining; but it frequently 

 exhibited an entirely normal appearance. 



Now and then a mouse was found in which the abdominal 

 cavity contained fresh blood, without my being able to discover 

 the source of the haemorrhage. The stomach and intestines 

 showed numerous alterations. Very frequently slight haemorrhage 



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