PATHOGENIC ANABROBIC BACILLI. 583 
serum may be seen. In agar plates, placed in a close receptacle 
from which oxygen is excluded, cloudy, dull-white colonies are 
formed which have irregular outlines and under the microscope 
are seen to be made up of branching and interlaced filaments radi- 
ating from the centre. Cultures of the malignant-cedema bacillus 
give off a peculiar, disagreeable odor, which cannot, however, be 
designated as ‘‘ putrefactive.” 
Pathogenesis.—Pathogenic for mice, guinea-pigs, rabbits, and, 
according to Kitt, for horses, dogs, goats, sheep, calves, pigs, chick- 
ens, and pigeons. According to Arloing and to Chauveau, cattle are 
immune. The disease is rarely developed except as a result of ex- 
perimental inoculations, but horses occasionally have malignant 
cedema from accidental inoculation, and cases have been reported 
in man—‘‘ gangréne gazeuse.” A small quantity of a pure cul- 
ture injected beneath the skin of a susceptible animal gives rise to 
an extensive inflammatory cedema of the subcutaneous connective 
tissue and of the superficial muscles, which extends from the point 
of inoculation, especially towards the more dependent portions of 
the body. The bloody serum effused is without odor and contains 
little if any gas. But when malignant edema results from the in- 
troduction of a little garden earth beneath the skin of a guinea-pig or 
other susceptible animal, the effused serum is frothy and has a pu- 
trefactive odor, no doubt from the presence of associated bacteria. 
Injections into the circulation do not give rise to malignant cedema, 
unless at the same time some bacilli are thrown into the connective 
tissue. While small animals usually die from an experimental in- 
oculation with a moderately small quantity of a pure culture, larger 
ones (dogs, sheep) frequently recover. At the autopsy, if made at 
once, the bacilli are found in great numbers in the effused serum, 
but not in blood from the heart or in preparations made from the 
parenchyma of the various organs; later they may be found in all 
parts of the body as a result of post-mortem multiplication. This 
applies to rabbits and to guinea-pigs, but not to mice ; in these little 
animals the bacilli may find their way into the blood during the last 
hours of life, and their presence may be demonstrated in smear prepa- 
rations of blood from the heart or from the parenchyma of the spleen 
or liver. In mice the spleen is considerably enlarged, dark in color, 
and softened ; in rabbits and guinea-pigs less so. With this excep- 
tion the internal organs present no very notable pathological changes. 
Animals which recover from malignant cedema are said to be 
subsequently immune (Arloing and Chauveai). Roux and Cham- 
berlain have shown that immunity may be induced in guinea-pigs by 
injecting filtered cultures of the malignant-cedema bacillus (about 
one hundred cubic centimetres of a bouillon culture in three doses) 
