ON EPIDEMICS AMONGST MICE. 309 



sequently, the danger of other animals becoming affected by 

 taking food infected by the bacillus is very slight. But in the 

 meantime, before commencing an experiment upon a large scale, 

 it would be necessary to make more extensive trial on animals of 

 the most different kinds, especially on all the species which are of 

 any importance to agriculture. 



But I must premise that many of the animals which are not 

 susceptible to the infection through their food, sicken and die 

 when inoculated with the bacilli hypodermically. I succeeded 

 with subcutaneous inoculation in the case of several rats, small 

 birds, pigeons, and guinea-pigs. In the case of the birds, an 

 extensive yellowish lardaceous infiltration was locally developed 

 at the point of inoculation in the thoracic muscles, which led to 

 necrotic separation of the diseased part. In this substance 

 I found enormous masses of bacilli. But I could not obtain any 

 from the liver of the dead animals by means of cultivation. They 

 died in from three to eleven days after inoculation. Rabbits 

 showed themselves to be only slightly susceptible. At the point 

 of inoculation only slightly sympathetic inflammation appeared, 

 or local discharges, which lasted for weeks, but finally healed up. 



From the foregoing observations, I hope that the new bacillus 

 typhi murium will give us a weapon which may be effectually 

 used against the Field Voles which cause so much damage to 

 agriculture. The best time for contending with them seems to 

 ine to be Spring, when the frosts are over, but before their food 

 has become very abundant. 



It is a very favourable circumstance that the bacillus retains 

 its vitality for a long time both in the wet and in the dry state. 

 Gelatine-cultures retain their vitality and infective properties 

 after being kept for six months. 



The question then arises, What is the origin of the epidemic ? 

 This question I cannot answer. The bacilli bear a certain 

 resemblance to those which I have found in pigeon-diphtheria ; 

 also to those of the pseudo-tuberculosis of rabbits and guinea- 

 pigs, which I discovered in 1883, when employed at the Hygienic 

 Institute, and which I have carefully studied and experimented 

 on; to the bacilli of the American and Danish swine-plague; to 

 the bacillus of ferret-disease, the bacillus of the spontaneous 

 rabbit-septicaemia of Eberth, the bacterium coli commune, and 

 other forms belonging to the group of typhus-bacilli. It might 



