BACILLUS OF BUBONIC PLAGUE. 607 
rhagic cases and shortly before death. It also occurs 
in the feces of men and animals. 
Morphology. Short thick rods, with rounded ends, 
frequently occurring in short chains and often sur- 
rounded by a capsule. When obtained from cultures 
the bacilli present considerable spherical enlargement 
(Fig. 82). 
Stains readily with the ordinary aniline dyes, the 
ends being usually more deeply colored than the central 
portion; does not stain by Gram’s method. 
Biological Characters. An aérobic, non-motile bacil- 
lus. Does not form spores. Grows on the usual culture 
media. Does not liquefy gelatin. Grows best on blood- 
serum in the incubator, the growth appearing on the 
surface after twenty-four to forty-eight hours, in the 
form of white, moist, transparent and iridescent col- 
onies. It grows rapidly on glycerin-agar, forming a 
grayish-white surface growth. In bouillon a very char- 
acteristic appearance is produced, the culture medium 
remaining clear while a granular or grumous deposit 
forms on the walls and on the bottom of the tube. 
Pathogenesis. This bacillus is pathogenic for rats, 
mice, guinea-pigs, monkeys, rabbits, flies, and other 
insects, which usually die within two or three days 
after inoculation. Then at the point of inoculation is 
found a somewhat hemorrhagic infiltration and cedema, 
with enlargements of the neighboring lymph-glands, 
hemorrhages into the peritoneal cavity and parenchy- 
matous congestion of the organs. The spleen sometimes 
shows minute nodules resembling miliary tubercles. 
Microscopically the bacilli are found in all the organs 
and in the blood. The disease is rapidly communicated 
from one animal to another, and thus its extension is 
