v PLAGUE IN THE EAT 109 



one or the other of these animals on subsequent testing 

 (by cutaneous inoculation) with virulent B. pestis 

 succumbed to plague, while the remainder proved them- 

 selves fully protected. Those insufficiently protected rats 

 died generally on the ninth or tenth day or even later. 

 The animals seemed lively till almost the evening preced- 

 ing death. On post-mortem examination it was invariably 

 found that they showed no bubo, the spleen was not 

 markedly enlarged and contained very few (if any) B. 

 pestis. The liver appeared unaltered, the heart's blood 

 contained no B. pestis in film specimens. But the lungs 

 always showed profound changes, varying, however, in the 

 different animals ; between red hepatisation of one or 

 more lobes in one or both lungs, and extensive white 

 necrotic patches, all intermediate conditions were found. 

 In all cases, however, the altered parts were literally 

 packed with B. pestis. Stained film specimens of the red 

 hepatised portions looked exactly like similar film 

 specimens of the juice of the lung in pneumonic plague 

 of man, described and illustrated in Chapter I. A similar 

 condition obtains also in the guinea-pig when insufficiently 

 protected by the plague prophylactic and afterwards 

 inoculated with virulent B. pestis. Here also the lungs 

 chiefly were found affected, showing all stages between 

 red hepatisation and extensive necrotic patches. The 

 affected parts are also literally filled with B. pestis. 

 I may add here that an experiment performed on monkeys 

 shows that this holds good also for the monkey, inasmuch 

 as one of the insufficiently protected monkeys, which 

 succumbed to plague on the eleventh day, showed distinct 

 evidence of pneumonia, patches of lung being in the state 

 of red hepatisation, others already showing commencing 



