74 OEIENTAL PLAGUE chap. 



tunity of experimenting for purposes of studying the 

 new plague prophylactic (which I described in a pre- 

 liminary report to the Local Government Board, 

 December 19, 1905) on a large number of white rats. 

 Amongst these (two hundred odd), I have seen at different 

 times spontaneous deaths in about half - a - dozen ; on 

 post-mortem examination they exhibited the caseous 

 necrotic patches in the lungs (chiefly of the upper lobes), 

 due to the presence of masses of the B. muris. 



6. Bacterium diphtheroides of Mice. — For completeness' sake I add 

 here the description of a microbe which distinctly belongs to the 

 group of diphtheroid bacilli, is indeed closely related, if not identical, 

 with the preceding B. muris, and therefore in morphology and by 

 positive Gram staining can be readily distinguished from B. pestis ; 

 as on several occasions I have met with it in mice, it might not 

 be out of place to mention this microbe here, as it is pathogenic 

 to mice, and as these animals are very useful and often used in 

 experimental and diagnostic work for plague. 



The history of this pathogenic diphtheroid microbe is as 

 follows : — 



A guinea-pig had been inoculated cutaneously on February 18, 

 1905, with a trace of an agar culture (forty -eight hours old) of 

 B. pestis derived originally from the spleen of a rat dead of plague. 

 The guinea - pig was found dead on February 22 (fifth day). 

 On post-mortem examination it showed large hemorrhagic bubo 

 crowded with B. pestis; almost the whole of the intestine showed 

 numerous petechie in the serous coat ; both testes showed the 

 superficial lymphatics injected with blood ; the pelvic lymph gland 

 was enlarged and hemorrhagic j the spleen was large, mottled with 

 grey nodules and crowded with B. pestis; the liver was pervaded 

 by whitish punctiform nodules ; the suprarenals were hemorrhagic. 

 From this it follows that the guinea-pig had died of typical subacute 

 plague. The spleen and the bubo of this guinea-pig were finely 

 minced, and a small amount of this material was placed on bits of 

 cloth, which were then kept under a bell jar and left to dry at the 

 temperature of the laboratory. On March 8, i.e. after fourteen 

 days' drying, some of the dry particles were taken off the cloth 

 and rubbed down in sterile distilled water, and from this emulsion 



