302 THE ZOOLOGIST. 



tint. In sweetened peptonized bouillon thej* grew very strongly. 

 They rendered it turbid with the gas engendered, and then 

 formed a thick cloudy layer on the surface. The previously 

 neutral reaction of the bouillon now became rather strongly acid. 

 The presence of alcohol in the distillation was proved by the 

 iodine test. 



The bacilli also developed well in milk. The appearance of 

 the milk was not altered dtiiing their growth, but the reaction 

 became rather strongly acid. 



On examining sections of the organs, I found the bacilli 

 generally arranged in masses within the capillaries. They formed 

 masses, like those in human typhus. Now and then single 

 specimens were seen in the capillaries ; they often lay within 

 them like large colourless cells. The yellowish spots in the liver, 

 which were often perceptible to the naked eye, contained no more 

 liver-tissue, and were generally surrounded by disintegrated 

 matter. There was always a mass of bacilli in the centre of these 

 portions. It appeared as if the bacilli had caused the disappear- 

 ance of the liver-cells, and disintegration. In other places the 

 masses lay in the normal tissue, without causing disintegration. 

 The mesenteric glands were pervaded with enormous masses of 

 bacilli. The appearances rather reminded me of those which 

 I had obtained after inoculating mice with the bacilli of pigeon- 

 diphtheria (Taubendiphtheriebaccillen) . 



The bacillus belongs indubitably to the group of typhus-like 

 bacilli of which a considerable number are already known. As it 

 has most resemblance to human typhus-bacillus, I propose to call 

 it the bacillus of mouse-typhus (Bacillus typhi murium). 



As regards the mode of infection, in this epidemic, it is 

 undoubtedly caused by infection through the digestive organs. 

 This is abundantly proved by the alterations in the small 

 intestine, and in the mesenteric glands. I cannot positively 

 affirm that the infection is caused entirely by nibbling a com- 

 panion who has died of the disease. In a number of mice which 

 I examined with all care I found bacilli in the contents of the 

 intestine. I think it not improbable that living bacilli which 

 have been evacuated with the f'ceces may get mixed with the food, 

 and be thus swallowed by other mice. Young mice especially, 

 which as a rule took no part in gnawing at the corpses, might 

 have become infected by foul food. The possibility of infection 

 by inhalation had also to be considered. 



