iv MICEOBES SIMULATING THE B. PESTIS 71 



microbe pathogenic for certain rodents. This B. myxoides, which 

 morphologically and in staining presents a certain resemblance to 

 Bacillus pestis, has cultural characters sufficiently distinct to differ- 

 entiate it from the plague bacillus. 



5. Bacterium muris. 1 — For some time back I have 

 kept white rats — half-grown and adult — in my laboratory. 

 They are generally in couples in clean and specially made 

 cages. 



On July 21 one of a couple of such rats was found 

 dead. It had been observed to be ailing some days 

 previously : its coat being rough, its breathing rapid, 

 and the animal showing somnolence. 



On post-mortem examination the following condition 

 was found : — A portion of the left and the whole of 

 the right lung were dark red. These portions were 

 consolidated and sank in water ; when cut into they 

 appeared solid ; there was caseous matter in the bronchi. 

 The spleen was not enlarged. No swollen lymph glands 

 could be found. The small intestine was congested, 

 relaxed, and contained mucus and numerous gas bubbles. 

 Film specimens made from the inflamed portions of the 

 lungs showed numerous large and small masses of 

 cylindrical and even filamentous bacilli. These when 

 stained in methylene-blue exhibited pronounced meta- 

 chromatism just like the diphtheria bacilli. Sections 

 through the hardened lungs showed that the consolida- 

 tion was due to distension of the alveoli, infundibula, 

 and bronchi by fibrinous exudation ; the latter containing 

 numerous leucocytes and coloured blood corpuscles, and, 

 as well, connected masses of the above bacilli. Cultiva- 

 tions made of the inflamed lung tissue yielded pure 



1 Report of Medical Officer, 1902-1903, p. 418 and passim. 



