THE PLAGUE BACILLUS 473 



hsemorrhagic oedema at the seat of inoculation, enlarge- 

 ment and congestion of the spleen, and enlargement of, 

 and haemorrhages into, the inguinal and axillary lymphatic 

 glands. If the animal live six or seven days, the glands 

 may be as large as small nuts (see some admirable prepara- 

 tions in the College of Surgeons Museum). The spleen 

 may be enormous, six times its natural size, and studded 

 with small yellowish nodules resembling miliary tubercles, 

 consisting of necrotic areas with masses of bacilli (Fig. 46) ; 

 the lungs also may be more or less inflamed, and contain 

 small and large necrotic foci. The bacilli are extremely 

 numerous at the seat of inoculation, in the glands, and 



FIG. 46. Spleen of guinea-pig inoculated with plague. 

 (Nat. size.) 



in the spleen, less so in the peritoneal fluid, liver, and 

 blood ; if the death of the animal is delayed the exudation 

 in the bronchi may contain considerable numbers. Some 

 bacilli may generally be found in the duodenum, trachea, 

 and larynx. Mice usually die in from two to three days, 

 and rats in from three to seven days after inoculation. In 

 rats and mice the post-mortem appearances are similar 

 to those in the guinea-pig. Rabbits are much less sus- 

 ceptible to plague than guinea-pigs but much depends 

 upon the virulence of the strain. A very small dose of 

 a pure culture may fail to kill an inoculated animal. Rats 

 can be infected by feeding on the corpses or carcases of 

 men or animals dead from the disease. 



In man the bacilli are found in large numbers in the 



