BACILLUS ABORTUS 415 
There is edema, leukocytosis, and the peritoneal fluid, increased in 
amount, swarms with the bacilli. Rabbits are less susceptible; rats 
and mice are relatively refractory. The subcutaneous injection of 
cultures of the organism, especially if the virulence is not great, leads 
to a chronic, wasting infection which usually terminates fatally. The 
subcutaneous tissue becomes edematous and necrotic, and ulceration 
frequently occurs. 
Human. — Besides the focal lesions, abscesses, ulcers, otitis media, 
less commonly liver abscesses, and bronchopneumonia, B. pyocyaneus 
occasionally produces severe gastro-intestinal infection, especially in 
young children, generalized sepsis, and inflammation of serous surfaces, 
the pleura, i)ericardium, and peritoneum.' B. pyocyaneus was found 
occasionally in wounds made by bullets and projectiles. 
Immunity and Immunization.— It is possible to immunize animals 
both by the cautious injection of the bacilli, which stimulates the for- 
mation of specific bacteriolysins, and by filtrates of broth cultures of 
the organisms, which incite the formation not only of bacteriolytic 
substances, but antitoxic substances as well. No practical use is 
made of these antibodies in human infections, however. 
Bacteriological Diagnosis.— Wounds infected by B. pyocyaneus are 
usually diagnosed by the blue-green color of the dressings. The bacilli 
are readily isolated upon gelatin plates, where the development of the 
blue-green color is very characteristic. 
BACILLUS ABORTUS. 
Historical. Infectious abortion is a disease which has for many 
years })een recognized as an important economic one in the cattle 
industry. Later it was found that the same disease also exists among 
horses, goats and sheep. The organism was first isolated by Bang.- 
Morphology.- B. abortus is a small pleomorphic bacillus, measuring 
0.4 to ().(') micron in diameter, by 0.6 to 2.5 microns in length. It 
occurs singly and in pairs; rarely short chains of three to six elements 
are found. The shape varies: some organisms are almost spherical, 
others are distinctly rod-shaped, the latter being more frequently 
found in broth cultures and in vivo. According to Preisz,^ branched 
forms may be found in older cultures. It is non-motile and pos- 
sesses no flagella, although Brownian movement may be fairly active. 
It possesses no capsules, and no spores have been demonstrated. 
It stains readily with ordinary anilin dyes, but somewhat irregularly, 
some areas staining more intensely than others. Occasionally with 
the methylene blue stain the organisms may present a bipolar appear- 
ance. The organism is Gram-negative. 
Isolation and Culture. —Initial growths on artificial media outside 
the animal body are somewhat difficult to obtain. The organism 
1 Waite: Jour. Infec. Dis., 1908, 5, 542. 
2 Ztschr. f. Thiermedizin, 1897, 1, 241, 258. 
3 Centralb. f. Bakteriol., orig., 1903, 33, 190. 
