v PLAGUE IN THE RAT 105 



sections of the hardened material show, the gland tissue 

 contains effused blood in both the cortical and medullary 

 lymph sinuses, while larger or smaller groups of B. pestis 

 are detectable in this effused blood. The juice of the 

 gland shows also crowds of the typical plague bacilli 

 readily stainable bipolarly in fuchsin (see Fig. 6). 

 The spleen is much enlarged, dark, and firm ; it is 

 not juicy. Stained film specimens from it show 

 crowds of bipolar -stained B. pestis (see Fig. 4). The 

 lungs are more or less congested and show occasionally 

 petechise. The heart - blood contains sometimes very 

 numerous, at other times only fairly numerous B. pestis, 

 as shown by cultures. The intestines and mesenteric 

 glands are congested, the small intestines being relaxed 

 and containing blood-stained mucus. In this mucus B. 

 pestis can be demonstrated by stained film specimens, as 

 also by culture of a particle of the mucus distributed in 

 sterile salt solution and then employed for making agar 

 surface plates, or, and this is a method which is equally 

 certain of positive result in a case in which the above 

 condition of the intestine obtains, by injecting a little 

 of the intestinal mucus subcutaneously, or, better still, 

 by inoculating it cutaneously into guinea-pigs or into rats. 



It is necessary to emphasise an important fact, viz. 

 that in whatever way (subcutaneously or cutaneously) the 

 rat is infected, the abdominal viscera, including the intes- 

 tines and mesenteric glands, generally participate in the 

 disease. For this reason the presence of the lesions in the 

 intestines and mesenteric glands may not be interpreted 

 as due to infection by food. 



The above is the condition in the rat which generally 

 obtains at the end of three days when the animal has been 



