vii INFECTION OF ANIMALS WITH PLAGUE 169 



tended, with extravasation of blood en masse, and with 

 B. pestis everywhere ; the mucosa over and around the 

 lymph follicles was filled with extravasated blood. Both 

 the tissue of the mucosa and that of the lymph follicles 

 were necrotic ; the lymph vessels and sinuses in the mucosa 

 and submucosa were distended and filled with continuous 

 masses of B. pestis. Necrotic patches were found in the 

 mesenteric glands, in the liver and in the spleen asso- 

 ciated with masses of B. pestis. 



Guinea-pig No. 9, which had been kept in the same 

 cage as guinea-pig No. 8, remained alive. On May 30 it 

 was injected subcutaneously with a trace of gelatine 

 culture of the heart's blood of its dead companion, guinea- 

 pig No. 8. It died on the seventh day with all appear- 

 ances of subacute plague : necrotic bubo ; liver and spleen 

 full of minute necrotic points ; lungs congested with 

 necrotic patches. 



Film specimens and cultures were made of the bubo, 

 the spleen, and the lung, and these showed copious 

 presence of B. pestis. 



This experiment is instructive in that it bears out a 

 fact on which in former reports I have repeatedly insisted, 

 viz. that of two animals kept together in one cage, one 

 may succumb to plague — its intestine, kidney, spleen, and 

 blood in general literally swarming with B. pestis, — 

 whereas its companion may remain, and this notwith- 

 standing blood-sucking insects with which guinea-pigs are 

 well provided, quite unaffected. If after twenty days the 

 animal which has thus escaped illness be inoculated with 

 B. pestis derived from its dead companion, it promptly 

 succumbs to plague. 



Experiment 5. — Two mice, Nos. 1 and 2, were fed on 



