548 THE ANAEROBIC BACTERIA 
but leads also to the formation of a small amount of gas and to con- 
siderable necrosis of the parenchymatous organs. The edematous, 
tissue lacks the characteristic pink color produced by the Welch bacillus 
infection, however. 
Serological Reactions.— Agglutinins of comparatively low potency 
may be obtained by injecting the washed bacilli into animals. The 
organisms exliibit rather marked racial specificity of agglutination, 
although all strains are clumped at lower dilutions of serum. Weinberg 
and Seguin state that many strains of B. oedematiens exhibit a decided 
tendency to agglutinate spontaneously. Hemolysin of comparatively 
low potency is found among the constituents of the soluble poison. 
Bacteriological Diagnosis.— Bacilli, which are relatively thick and long, 
and usually somewhat curved, and which take the Gram stain, are 
immediately suggestive of B. oedematiens, especially if the material is 
obtained from pathological sources. 
Cultural.— The absence of striking characteristics, as stormy or 
delayed fermentation, the liquefaction of gelatin (strict anaerobic 
conditions) and gas production in glucose, but not lactose, saccharose 
or mannitol, is a strong indication of the presence of the organism. 
jSerofor/tVa/.- Complement-fixation is not dependable. Hemolysis of 
erythrocytes is not characteristic. Agglutination with specific sera and 
the marked tendency toward auto-agglutination is the most distinc- 
tive serological reaction. 
The injection of pure cultures, containing both bacilli and toxic pro- 
ducts, should induce gelatinous edema with but small amounts of gas 
in rabbits or guinea-pigs in order to suggest the pathology of B. 
oedematiens. It shoukl be emphasized that pure cultures alone will 
induce the characteristic edema; the pallor of the visceral organs at 
autopsy and the recognition of the morphology of the bacillus are 
additional diagnostic features. 
BACILLUS HISTOLYTICUS. 
Bacillus histolyticus, described by Weinberg and wSeguin^ in 1915, 
possesses the remarkable property of digesting injured or pathological 
tissue in the living animal by means of a soluble proteolytic enzyme. 
Unlike B. sporogenes, which also possesses this power to a lesser degree, 
B. histolyticus also possesses toxicogenic powers. 
Morphology. — B. histolyticus is a rod-shaped bacillus with rounded 
ends, which measures on the average from 0.5 to 0.8 micron in diameter 
and from 2 to () microns in length. The organisms very commonly 
occur in pairs, less frequently in short chains. Ordinarily the bacilli 
are straight but occasionally the longer forms exhibit slight curving 
along the greater axis. 
Young cultures, and those freshly isolated from pathological tissues 
1 Compt. rend. Soc. de biol., 1915, 78, 274; ibid.. 1917, 80, 157, 
