118 OMENTAL PLAGUE chap. 



firm, and containing crowds of B. pestis ; kidney and liver 

 large and much congested ; both lungs much congested. 

 Heart's blood yielded crowds of colonies of B. pestis in 

 pure culture. 



It is clear from the above that this strain of B. pestis 

 ( Cardiff bubo) is of normal and high virulence ; and I 

 may add that colonies of the microbe in their early 

 phases of culture on gelatine were of the typical angular, 

 granular, " opaque" kind, and that the bacilli from them 

 were of the typical cylindrical form ; that is to say, this 

 strain is in respect of virulence and in all its morphological 

 and cultural characters a good representative of the type 

 No. 1 (human). 



In contrast with the B. pestis (type No. 1) of 

 experiments 5 and 6, I pass to further experiments with 

 the attenuated B. pestis of the second or rat type, 

 derived from the inguinal gland of the Haffkine protected 

 rat already referred to earlier. B. pestis of this type is in 

 culture shorter than that of type No. 1, and it forms in 

 the earlier phases of its growth on gelatine less angular 

 and more rounded colonies, the growth on the gelatine 

 being at the same time more translucent and less 

 granular. These characters have now become permanent 

 through many subcultures. The difference between the 

 two types here dealt with — viz. the strain of Cardiff 

 bubo (human type) and the strain of protected, rat (rat 

 type) — is so distinct that, on looking at streak as also 

 stab cultures, or at plate cultures on gelatine of the two 

 strains under exactly the same conditions, the distinction 

 during the first three or four days cannot be missed. I 

 have repeatedly asked colleagues to inspect with a glass 

 a number of parallel cultures of the two strains, and 





