i THE ESSENTIAL CAUSE 13 



kept for some minutes in a watch-glass, bipolar bacilli 

 could be found in the sediment. 



Cultures made of the spleen, lymph (inguinal) gland, 

 kidney, liver, and lung, all produced a crop of typical 

 colonies of B. pestis, most abundant in the case of the 

 spleen and heart's blood. 



From this it follows that the form of plague of which 

 these rats had died was the septicsemic form, viz. conges- 

 tion of the viscera — particularly the spleen, lymph glands, 

 and lungs — with general distribution of B. pestis in the 

 circulation. 



The distribution in and effects of B. pestis on 

 rodents infected with materials containing B. pestis 

 are subject to certain variations, which will be considered 

 fully later in connection with the experimental production 

 in various ways of plague in these animals ; we proceed 

 now to consider the morphology, cultural characters, and 

 experimental effects of the B. pestis. 



