76 ORIENTAL PLAGUE chap. 



The microbe in question shows the morphological characters of 

 the B. diphtheria of the short variety, it gives but feeble Neisser 

 granules, and it does not act fatally on guinea-pigs or mice, be the 

 injected dose large or small. The microbe, as stated just now, is 

 strongly Gram -positive, it produces acid in glucose broth after 

 forty-eight hours' incubation at 37° C. On gelatine at 21° C. its 

 growth is extremely retarded, not before the fourth day is there 

 a noticeable growth to be detected, and when it has started, the 

 colonies are and remain very minute and very translucent. In this 

 respect it differs both from the true B. diphtherial and from the 

 B. muris. On account of its action on the guinea-pig being similar 

 to that of B. muris — causing the gradual formation of abscess — and 

 on account of its having been obtained from the mouse, I conclude 

 that it is the B. muris, or a variety of the microbe obtained from the 

 lung of rats (see previous pages) ; but the diphtheroid microbe of 

 the mouse is shorter, gives but feeble Neisser, and grows much more 

 slowly on gelatine than the typical B. muris of the rat. I do not 

 think the two are quite identical, although it must be inferred that 

 they are clearly different varieties closely related to one another. 

 I am confirmed in this by the result of their culture in different 

 sugar media. 



Dr. Gordon informs me that both the B. muris of the rat and 

 the diphtheroid bacillus of the mouse exhibit exactly the same 

 reactions in the different sugared media — reactions which not only 

 prove their mutual relation, but distinguish them from the B. 

 diphtheria}. 



The question of interest is, Whence is derived the diphtheroid 

 microbe — B. muris — of the mouse ? Was it present in the organs 

 (bubo and spleen) of the guinea-pig dead of subacute plague ; was 

 it present in the cloth on which the particles of those plague organs 

 had been dried ; or was it present in the skin of the experimented 

 mice, and carried during the subcutaneous injection of the emulsion 

 into the subcutaneous tissue, where, owing to the inflammatory effect 

 of the plague toxin, it multiplied ? 



