iv MICKOBES SIMULATING THE B. PEST1S 53 



in the hanging drop, was seen to consist of motile bacilli. 

 The extent of the filmy growth — covering the greater part 

 of the surface of the plate after twenty-four hours' incuba- 

 tion — was alone sufficient to negative B. pestis ; add to 

 this that the bacilli were motile. But a bacteriologist of 

 insufficient experience — and the number of these who 

 perform bacteriological analytical work has of late years 

 greatly increased — might have been misled by the trans- 

 lucent viscid growth (ground-glass-like) ; further, omitting 

 to examine the growth in the living state — an omission 

 not infrequent — and therefore not noticing the motility 

 of the component bacilli, might (and generally does) at 

 once proceed to prepare stained film specimens. In these 

 he would notice that most of the bacilli show bipolar 

 staining, just like B. pestis ; moreover, he would ascertain 

 that they are Gram-negative, and he might well sustain 

 and express what appears to him a justifiable suspicion, 

 that he is dealing with B. pestis. The guinea-pig injected 

 with the original material did not show after twenty -four 

 hours any noticeable bubo, nor did it after forty-eight 

 hours, but this might perhaps be thought to be due to the 

 material containing only very few of the incriminated 

 bacilli ; he therefore would proceed to inject subcutaneously 

 a fresh guinea-pig in the groin with a larger — considerable 

 — amount of the filmy growth from the agar plate. This 

 second guinea-pig shows next day a decided gelatinous 

 swelling about the groin, and the animal is quiet and a 

 little off feed. If the guinea-pig is killed, the subcutaneous 

 tissue of the thigh, groin, and flanks appears greatly 

 congested and infiltrated with sanguineous fluid ; when a 

 drop of this is examined in the fresh state it shows 

 numerous actively motile bacilli ; but if, as not infrequently 



