vii INFECTION OF ANIMALS WITH PLAGUE 195 



subacute plague which had been cut up in small bits and 

 kept over sulphuric acid for seven days were by this 

 time perfectly dry and hard. Two rats were fed with 

 this material. Both animals remained unaffected ; so they 

 were at the end of a week injected cutaneously with agar 

 culture (twenty -four hours old) of B. pestis derived 

 from a recent case of plague in man (case from s.s. 

 Weybridge) which had been landed at Denton in 

 December 1904, Both were dead of acute plague in 

 three days. 



Experiment 21. — The organs (bubo, spleen, liver, and 

 lungs) of two rats, dead of plague after having been in- 

 oculated cutaneously with the blood of a guinea-pig dead 

 of acute plague, were cut up into small bits and dried 

 over sulphuric acid for eight days. With this material, 

 by this time quite dry and hard, two wild rats were fed. 

 Both animals remained unaffected. 



Experiment 22. — The organs of a guinea-pig dead on 

 February 22 of acute plague were cut up into bits and 

 dried over sulphuric acid for forty-eight hours. By this 

 time the outside of the material was well dried, though 

 the inside remained still moist. With this material two 

 tame rats in one cage, and two wild or sewer rats in a 

 second cage, were fed on February 24. 



One of the sewer 1 rats was found dead on February 

 28, the other remaining, by then and afterward, seemingly 

 unaffected. Both tame rats at this date seemed ill, and 

 showed rough coats. The post-mortem examination 

 of the dead sewer rat showed the following condi- 

 tions : — The greater part of the lower ileum congested, 



1 The wild rats used in these experiments were all of the common brown sewer 

 rat type. 



