232 BACILLI OF THE HEMORRHAGIC SEPTICEMIA GROUP 



In a healthy rat the only glands which are large enough to be seen 

 easily are those forming the crescent embracing the salivary glands 

 in the submaxillary region, and the elongated retroperitoneal glands 

 on each side of the middle line in the lower part of the abdomen. 

 The latter are called the pelvic glands. In the bubonic type of plague 

 the glands affected and presenting the picture of the typical plague 

 bubo described above are in the order of frequency of infection, 

 according to the Bombay figures : Glands of the neck (75 per cent.), 

 glands of the axilla (15.1 per cent.), glands of the groin (6.1 per cent.), 

 glands*of the pelvis (3.8 per cent.). A bubo in a plague-infected rat 

 feels hard when cut across, but it has not the tough consistency of a 

 normal gland. The contents of the latter are not easily squeezed out 

 by pressure, while in a bubo the substance of the gland is readily 

 broken down by slight pressure with the forceps. A bubo on section 

 has the appearance of necrosis, affecting first the medullary portion 

 of the gland and gradually spreading outward, so that ultimately the 

 gland may be converted into a mass of necrotic tissue enclosed 

 within the capsule. The central portion consequently appears gray, 

 and at a later stage the centre breaks down into a rather dry, very 

 rarely a liquid, purulent material. Buboes with greenish liquid pus 

 are not typical of plague. 



The presence of a typical bubo is the most important sign of plague 

 in rats, and next in importance is the so-called granular liver. Accord- 

 ing to the Bombay findings, it is only met with in rats infected with 

 plague. The liver appears to be in a condition of fatty degeneration, 

 but, as a matter of fact, the changes are not fatty but necrotic. The 

 outlines of the lobules are distinct and the surface of the organ presents 

 numerous gray or whitish granules of the size of a pinpoint, which 

 give the liver a stippled appearance as if it had been dusted over with 

 gray pepper. This appearance has given rise to the term granular 

 liver. The gray areas may be so small that only the closest scrutiny 

 of an experienced observer will detect them. When larger the granules 

 are of a yellow color and vary somewhat in size. In a typical case 

 the granules are not raised above the surface of the liver. The spleen, 

 which is very typically changed in experimental plague in guinea-pigs, 

 is not very characteristically changed in rat plague, though it is gener- 

 ally markedly enlarged. One of the most important postmortem 

 findings in the disease is the presence of an abundant clear pleural 

 effusion. Hemorrhages, both subcutaneous, subperitoneal, and in 

 the internal organs, are likewise constant and important pathologic 

 changes in rat plague. 



McCoy has recently published the results of the investigation of 

 rat plague in California, and his findings on comparatively small 

 material, in general, agree well with the Bombay findings. However, 

 in the American material the bubo was generally found in the groin 

 and not in the cervical glands. Since the quantity of material exam- 

 ined in California is only about 1 per cent, of the material examined 



