30 ORIENTAL PLAGUE chap. 



inversely proportional to the duration of the disease — 

 the fluid is densely packed with B. pestis embedded in a 

 gelatinous ground substance, many of the B. pestis forming 

 shorter or longer chains. Staining film specimens, the 

 bipolar nature of the individual bacilli is well brought out, 

 as also the gelatinous ground substance, which here and 

 there may be mistaken for a special capsule enveloping 

 the bacilli (see a former page). 



The viscid nature of the exudation together with the 

 dense aggregation of bipolar bacilli, many of them in 

 longer or shorter chains, may be considered as fairly 

 characteristic for plague ; but it is not absolutely so, since 

 we shall mention some other microbes which, under similar 

 conditions, produce similar results. 



Cutaneous inoculation of mice, rats, and guinea-pigs 

 causes the disease with certainty. The great value of 

 cutaneous inoculation, which was practised by the Austrian 

 Plague Commission, lies principally in this, that very 

 small amounts can be used for infection with positive 

 results ; leaving out malignant anthrax, and one or two 

 others, B. pestis is one of the few microbes which cause 

 acute disease in rodents when applied in minute doses to 

 a scratch or a surface incision of the cutis, or is merely 

 rubbed into the cutis. This shows that the B. pestis 

 readily and rapidly multiplies in the skin ; at the same 

 time, as far as mice, rats, and guinea-pigs are concerned, 

 when inoculated into the skin the B. pestis does not lose 

 anything of its virulence. 



As regards mice and rats I proceed in the following 

 manner : — The hairs are cut off with scissors from the skin 

 of the dorsum at the root of the tail ; with the point of a 

 scalpel which is previously dipped into plague material 



