v PLAGUE IN THE EAT 95 



the Cardiff rat in — (a) lesser virulence towards the 

 guinea-pig ; (b) rapid loss of virulence on cultivation in 

 the laboratory ; and (c) that in cultural respects it was 

 more of the rat B. pestis. 



Before giving a further detailed account of the cultural 

 and experimental results obtained with the above rat- 

 plague bacillus, I wish to introduce here some observations 

 bearing on the same subject made with cultures sent to 

 me by Dr. Edington of the Cape of Good Hope. 



Dr. Edington, it will be remembered, not only 

 doubted, but actually denied, that the mortality which 

 had occurred amongst the rats of Cape Town and Simon's 

 Bay early in the occurrence of human plague in these 

 places was real plague. He described it as a separate 

 specific disease of the rat, and placed it along with 

 hemorrhagic septicaemias such as swine fever, fowl cholera, 

 etc. According to Edington, the microbe which caused 

 this rat disease was distinctly different both morpho- 

 logically and culturally from B. pestis ; moreover, the 

 action of cultures, as also of original morbid tissues, on 

 rodents differed from, in that it was considerably less 

 effective than, that of true plague. Dr. Edington was 

 kind enough to send me on two different occasions agar 

 cultures of the microbe in question, as also stained film 

 specimens. I have with these cultures made a con- 

 siderable number of observations — by culture and by 

 experiment — and I am of the opinion that the microbe in 

 question is no other than B. pestis. It has, however, to 

 be added that in the state in which it reached me this 

 microbe certainly presented both in morphological and 

 cultural respects those peculiarities which Dr. Edington 

 had seen and described; and further, as mentioned by 



