iv MICROBES SIMULATING THE B. PESTIS 81 



causes no haemorrhage or cedema in the surrounding tissue; the 

 enlargement commences in two or three days, and by the end of the 

 week — at the earliest — the gland has been converted into an abscess. 

 Injected in small doses intraperitoneally it does not cause acute peri- 

 tonitis and death in a day or two with viscid copious exudation as 

 B. pestis does ; for with B. pseudo-tuberculosis death occurs not earlier than 

 seven or eight days, generally later ; on post-mortem examination the 

 omentum and the pancreas are thickened, and contain smaller and larger 

 firm nodules with purulent caseous centre. The necrotic nodules of the 

 spleen, liver, and lung are typical in their occurrence in guinea-pigs 

 injected subcutaneously with B. pseudo-tuberculosis ; they are found 

 after death of the animal, i.e. after seven days, generally between nine 

 and sixteen days' duration of the illness. I have repeatedly pointed 

 out that necrotic nodules in the spleen, liver, and lung of guinea-pigs 

 occur also when these animals are injected subcutaneously with 

 B. pestis of subnormal virulence, and that they constantly occur in 

 them when inoculated cutaneously, but the time in which they 

 appear is very much shorter than with B. pseudo-tuberculosis. 



The morphological and cultural characters of B. pseudo- 

 tuberculosis I have described in detail in the Keports of the Medical 

 Officer of the Local Government Board, 1899-1900 ; those of B. pestis 

 on a previous page ; and I will here summarise the essential differences 

 only :— 



(1) In the affected organs the B. pseudo -tuberculosis occurs 

 generally within cells, e.g. in those of the nodules of the omentum 

 and pancreas j it is shorter than the B. pestis, does not stain so 

 readily as the latter, and does not show the typical bipolar staining. 



(2) Taken from culture B. pseudo-tuberculosis shows feeble Gram 

 staining. 



(3) B. pseudo-tuberculosis grows much faster on agar and its 

 colonies are decidedly less translucent, being more whitish than 

 those of B. pestis. 



(4) B. pseudo-tuberculosis on gelatine forms colonies decidedly more 

 translucent than B. pestis, and they are not granular, or distinctly less 

 so than those of B. pestis. 



(5) Particles of agar culture of B. pseudo-tuberculosis emulsify 

 readily in saline solution or bouillon ; those of B. pestis, as mentioned 

 in a former chapter, are viscid and do not emulsify readily. 



(6) In broth B. pseudo-tuberculosis forms in a week a distinct 

 pellicle, at any rate at the rim of the surface. B. pestis does not do so. 



G 



