iv MICKOBES SIMULATING THE B. PESTIS 55 



Eats are peculiar in this respect, that even a short 

 time after death — in the warm part of the year, in less 

 than twelve hours — the spleen may swarm with proteus, 

 obviously derived from the intestine. Stained film 

 specimens of such a spleen always show more or less 

 numerously — particularly in the outer portions of the 

 organ — oval bacilli with bipolar appearance. These 

 bacilli under culture prove to be Proteus vulgaris : an 

 agar surface plate shows already, after twenty-four hours 

 and less, a filmy, translucent, rapidly spreading growth ; 

 when examined in the hanging drop the growth is com- 

 posed of actively motile bacilli ; when stained, many 

 exhibit bipolar staining ; gelatine is liquefied by the 

 growth. The bacilli of this growth are virulent for the 

 guinea-pig : when an emulsion of the rat spleen — if con- 

 taining abundance of these bacilli — or when a portion of 

 the agar growth is injected subcutaneously into the groin 

 of a guinea-pig, it will be found that the animal shows 

 after twenty-four hours extensive hemorrhagic infiltra- 

 tion of the subcutaneous tissue, the exudation being 

 crowded with Proteus vulgaris — actively motile rods, 

 Gram-negative, bipolar in staining. The animal may be 

 dead within thirty-six to forty-eight hours ; no bacilli are 

 found in the blood or spleen, but they abound in the local 

 infiltration. It is therefore obvious that, judging by mere 

 stained film specimens of the original spleen, or by the 

 fatal effect on the experimental guinea-pig, showing 

 hemorrhagic tumour about the seat of injection, contain- 

 ing abundance of bacilli which in stained films exhibit 

 bipolar staining, an error in diagnosis may be easily 

 committed. If a rat really had died of plague the bipolar 

 bacilli seen in the film specimens of its spleen will yield on 



