EXPERIMENTAL INOCULATION 437 



Spore formation occurs above 20 C., and is usually well seen 

 within forty-eight hours at 37 C. The spores have the usual 

 high powers of resistance, and may be kept for months in the 

 dried condition without being killed. 



Experimental Inoculation. A considerable number of animals 

 the guinea-pig, rabbit, sheep, and goat, for example are 

 susceptible to inoculation with this organism. The ox is said 

 to be quite immune to experimental inoculation, though it can, 

 under certain conditions, contract the disease by natural channels. 

 The guinea-pig is the animal most convenient for experimental 

 inoculation. When the disease is set up in the guinea-pig by 

 subcutaneous inoculation with garden soil, death usually occurs 

 in about twenty-four to forty-eight hours. There is an intense 

 inflammatory oedema around the site of inoculation, which 

 extends over the wall of the abdomen and thorax. The skin 

 and subcutaneous tissue are infiltrated with a reddish-brown 

 fluid and softened ; they contain bubbles of gas and are at places 

 gangrenous. The superficial muscles are also involved. These 

 parts have a very putrid odour. The internal organs are con- 

 gested, the spleen soft but not much enlarged. In such condi- 

 tions the bacillus of malignant oedema, both in short and long 

 forms, will be found in the affected tissues along with various 

 other organisms. Spores may be present, especially when the 

 examination is made some time after the death of the animal. 

 If the animal is examined immediately after death, a few of the 

 bacilli may be present in the peritoneum and pleurae, usually in 

 the form of long motile filaments, but they are almost invariably 

 absent from the blood. A short time after death, however, they 

 spread directly into the blood and various organs, and may then 

 be found in considerable numbers. 



Subcutaneous inoculation with pure cultures of the bacillus of 

 malignant oedema produces chiefly a spreading bloody oedema, 

 the muscles being softened and partly necrosed ; but there is 

 little formation of gas, and the putrid odour is almost absent. 



When the bacilli are injected into mice, however, they enter 

 and multiply in the blood stream, and they are found in con- 

 siderable numbers in the various organs, so that a condition not 

 unlike that of anthrax is found. The spleen also is much 

 swollen. 



The virulence of the bacillus of malignant oedema varies con- 

 siderably in different cases, and it always becomes diminished in 

 cultures grown for some time. A smaller dose produces a 

 fatal result when injected along with various other organisms 

 (bacillus prodigiosus, etc.). 



