PATHOGENIC ANAEROBIC 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-oedema 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 

 oedema from accidental inoculation, and cases have been reported 

 in man "gangrene gazeuse." A small quantity of a pure cul- 

 ture injected beneath the skin of a susceptible animal gives rise to 

 an extensive inflammatory oedema 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 oedema 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 oedema, 

 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 Chauveau). Roux and Cham- 

 berlain have shown that immunity may be induced in guinea-pigs by 

 injecting filtered cultures of the malignant-oedema bacillus (about 

 one hundred cubic centimetres of a bouillon culture in three doses) 



